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* [PATCH 0/6] Push negotiation
@ 2021-04-09  1:09 Jonathan Tan
  2021-04-09  1:09 ` [PATCH 1/6] fetch-pack: buffer object-format with other args Jonathan Tan
                   ` (7 more replies)
  0 siblings, 8 replies; 33+ messages in thread
From: Jonathan Tan @ 2021-04-09  1:09 UTC (permalink / raw)
  To: git; +Cc: Jonathan Tan

Here are patches for push negotiation. The basic idea is that we can
reuse part of the fetch protocol (and code) to find out what is in
common between the client and server, and then use that information to
further narrow the objects sent in the packfile during a push.

Patch 1 is a bug fix that probably should be merged even if the rest
aren't. Patches 2-4 are refactorings in preparation for the future
patches. Patches 5-6 contain the actual logic and documentation.

I have written more about it in my prior work [1], although the commit
messages and documentation in patches 5-6 should be enough to explain
what's going on. (If they're not, feel free to make review comments.)

The main change from [1] is that the client-side code that used to be in
builtin/fetch-pack.c is now in builtin/fetch.c, because I realized that
builtin/fetch-pack.c does not support HTTP. Other than that, all the
"what hasn't been done yet" items have been done except for statistics
in the commit message.

[1] https://lore.kernel.org/git/20210218012100.928957-1-jonathantanmy@google.com/

Jonathan Tan (6):
  fetch-pack: buffer object-format with other args
  fetch-pack: refactor process_acks()
  fetch-pack: refactor add_haves()
  fetch-pack: refactor command and capability write
  fetch: teach independent negotiation (no packfile)
  send-pack: support push negotiation

 Documentation/config/push.txt           |   7 +
 Documentation/technical/protocol-v2.txt |   8 +
 builtin/fetch.c                         |  27 ++-
 fetch-pack.c                            | 224 +++++++++++++++---------
 fetch-pack.h                            |  11 ++
 object.h                                |   2 +-
 send-pack.c                             |  61 ++++++-
 t/t5516-fetch-push.sh                   |  35 ++++
 t/t5701-git-serve.sh                    |   2 +-
 t/t5702-protocol-v2.sh                  |  89 ++++++++++
 transport-helper.c                      |  10 ++
 transport.c                             |  30 +++-
 transport.h                             |   6 +
 upload-pack.c                           |  18 +-
 14 files changed, 430 insertions(+), 100 deletions(-)

-- 
2.31.1.295.g9ea45b61b8-goog


^ permalink raw reply	[flat|nested] 33+ messages in thread

* [PATCH 1/6] fetch-pack: buffer object-format with other args
  2021-04-09  1:09 [PATCH 0/6] Push negotiation Jonathan Tan
@ 2021-04-09  1:09 ` Jonathan Tan
  2021-04-09  4:49   ` Junio C Hamano
  2021-04-09  1:09 ` [PATCH 2/6] fetch-pack: refactor process_acks() Jonathan Tan
                   ` (6 subsequent siblings)
  7 siblings, 1 reply; 33+ messages in thread
From: Jonathan Tan @ 2021-04-09  1:09 UTC (permalink / raw)
  To: git; +Cc: Jonathan Tan

In send_fetch_request(), "object-format" is written directly to the file
descriptor, as opposed to the other arguments, which are buffered.
Buffer "object-format" as well. "object-format" must be buffered; in
particular, it must appear after "command=fetch" in the request.

This divergence was introduced in 4b831208bb ("fetch-pack: parse and
advertise the object-format capability", 2020-05-27), perhaps as an
oversight (the surrounding code at the point of this commit has already
been using a request buffer.)

Signed-off-by: Jonathan Tan <jonathantanmy@google.com>
---
 fetch-pack.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/fetch-pack.c b/fetch-pack.c
index 6e68276aa3..2318ebe680 100644
--- a/fetch-pack.c
+++ b/fetch-pack.c
@@ -1251,7 +1251,7 @@ static int send_fetch_request(struct fetch_negotiator *negotiator, int fd_out,
 		if (hash_algo_by_ptr(the_hash_algo) != hash_algo)
 			die(_("mismatched algorithms: client %s; server %s"),
 			    the_hash_algo->name, hash_name);
-		packet_write_fmt(fd_out, "object-format=%s", the_hash_algo->name);
+		packet_buf_write(&req_buf, "object-format=%s", the_hash_algo->name);
 	} else if (hash_algo_by_ptr(the_hash_algo) != GIT_HASH_SHA1) {
 		die(_("the server does not support algorithm '%s'"),
 		    the_hash_algo->name);
-- 
2.31.1.295.g9ea45b61b8-goog


^ permalink raw reply	[flat|nested] 33+ messages in thread

* [PATCH 2/6] fetch-pack: refactor process_acks()
  2021-04-09  1:09 [PATCH 0/6] Push negotiation Jonathan Tan
  2021-04-09  1:09 ` [PATCH 1/6] fetch-pack: buffer object-format with other args Jonathan Tan
@ 2021-04-09  1:09 ` Jonathan Tan
  2021-04-09  5:08   ` Junio C Hamano
  2021-05-03 16:30   ` Derrick Stolee
  2021-04-09  1:10 ` [PATCH 3/6] fetch-pack: refactor add_haves() Jonathan Tan
                   ` (5 subsequent siblings)
  7 siblings, 2 replies; 33+ messages in thread
From: Jonathan Tan @ 2021-04-09  1:09 UTC (permalink / raw)
  To: git; +Cc: Jonathan Tan

A subsequent commit will need part, but not all, of the functionality in
process_acks(), so move some of its functionality to its sole caller
do_fetch_pack_v2(). As a side effect, the resulting code is also
shorter.

Signed-off-by: Jonathan Tan <jonathantanmy@google.com>
---
 fetch-pack.c | 70 +++++++++++++++++-----------------------------------
 1 file changed, 22 insertions(+), 48 deletions(-)

diff --git a/fetch-pack.c b/fetch-pack.c
index 2318ebe680..9f3901cdba 100644
--- a/fetch-pack.c
+++ b/fetch-pack.c
@@ -1351,35 +1351,11 @@ static int process_section_header(struct packet_reader *reader,
 	return ret;
 }
 
-enum common_found {
-	/*
-	 * No commit was found to be possessed by both the client and the
-	 * server, and "ready" was not received.
-	 */
-	NO_COMMON_FOUND,
-
-	/*
-	 * At least one commit was found to be possessed by both the client and
-	 * the server, and "ready" was not received.
-	 */
-	COMMON_FOUND,
-
-	/*
-	 * "ready" was received, indicating that the server is ready to send
-	 * the packfile without any further negotiation.
-	 */
-	READY
-};
-
-static enum common_found process_acks(struct fetch_negotiator *negotiator,
-				      struct packet_reader *reader,
-				      struct oidset *common)
+static int process_ack(struct fetch_negotiator *negotiator,
+		       struct packet_reader *reader,
+		       struct object_id *common_oid,
+		       int *received_ready)
 {
-	/* received */
-	int received_ready = 0;
-	int received_ack = 0;
-
-	process_section_header(reader, "acknowledgments", 0);
 	while (packet_reader_read(reader) == PACKET_READ_NORMAL) {
 		const char *arg;
 
@@ -1387,20 +1363,17 @@ static enum common_found process_acks(struct fetch_negotiator *negotiator,
 			continue;
 
 		if (skip_prefix(reader->line, "ACK ", &arg)) {
-			struct object_id oid;
-			received_ack = 1;
-			if (!get_oid_hex(arg, &oid)) {
+			if (!get_oid_hex(arg, common_oid)) {
 				struct commit *commit;
-				oidset_insert(common, &oid);
-				commit = lookup_commit(the_repository, &oid);
+				commit = lookup_commit(the_repository, common_oid);
 				if (negotiator)
 					negotiator->ack(negotiator, commit);
 			}
-			continue;
+			return 1;
 		}
 
 		if (!strcmp(reader->line, "ready")) {
-			received_ready = 1;
+			*received_ready = 1;
 			continue;
 		}
 
@@ -1418,13 +1391,12 @@ static enum common_found process_acks(struct fetch_negotiator *negotiator,
 	 * sent. Therefore, a DELIM is expected if "ready" is sent, and a FLUSH
 	 * otherwise.
 	 */
-	if (received_ready && reader->status != PACKET_READ_DELIM)
+	if (*received_ready && reader->status != PACKET_READ_DELIM)
 		die(_("expected packfile to be sent after 'ready'"));
-	if (!received_ready && reader->status != PACKET_READ_FLUSH)
+	if (!*received_ready && reader->status != PACKET_READ_FLUSH)
 		die(_("expected no other sections to be sent after no 'ready'"));
 
-	return received_ready ? READY :
-		(received_ack ? COMMON_FOUND : NO_COMMON_FOUND);
+	return 0;
 }
 
 static void receive_shallow_info(struct fetch_pack_args *args,
@@ -1573,6 +1545,8 @@ static struct ref *do_fetch_pack_v2(struct fetch_pack_args *args,
 	struct fetch_negotiator negotiator_alloc;
 	struct fetch_negotiator *negotiator;
 	int seen_ack = 0;
+	struct object_id common_oid;
+	int received_ready = 0;
 	struct string_list packfile_uris = STRING_LIST_INIT_DUP;
 	int i;
 	struct strvec index_pack_args = STRVEC_INIT;
@@ -1631,22 +1605,22 @@ static struct ref *do_fetch_pack_v2(struct fetch_pack_args *args,
 			break;
 		case FETCH_PROCESS_ACKS:
 			/* Process ACKs/NAKs */
-			switch (process_acks(negotiator, &reader, &common)) {
-			case READY:
+			process_section_header(&reader, "acknowledgments", 0);
+			while (process_ack(negotiator, &reader, &common_oid,
+					   &received_ready)) {
+				in_vain = 0;
+				seen_ack = 1;
+				oidset_insert(&common, &common_oid);
+			}
+			if (received_ready) {
 				/*
 				 * Don't check for response delimiter; get_pack() will
 				 * read the rest of this response.
 				 */
 				state = FETCH_GET_PACK;
-				break;
-			case COMMON_FOUND:
-				in_vain = 0;
-				seen_ack = 1;
-				/* fallthrough */
-			case NO_COMMON_FOUND:
+			} else {
 				do_check_stateless_delimiter(args, &reader);
 				state = FETCH_SEND_REQUEST;
-				break;
 			}
 			break;
 		case FETCH_GET_PACK:
-- 
2.31.1.295.g9ea45b61b8-goog


^ permalink raw reply	[flat|nested] 33+ messages in thread

* [PATCH 3/6] fetch-pack: refactor add_haves()
  2021-04-09  1:09 [PATCH 0/6] Push negotiation Jonathan Tan
  2021-04-09  1:09 ` [PATCH 1/6] fetch-pack: buffer object-format with other args Jonathan Tan
  2021-04-09  1:09 ` [PATCH 2/6] fetch-pack: refactor process_acks() Jonathan Tan
@ 2021-04-09  1:10 ` Jonathan Tan
  2021-04-09  5:20   ` Junio C Hamano
  2021-04-09  1:10 ` [PATCH 4/6] fetch-pack: refactor command and capability write Jonathan Tan
                   ` (4 subsequent siblings)
  7 siblings, 1 reply; 33+ messages in thread
From: Jonathan Tan @ 2021-04-09  1:10 UTC (permalink / raw)
  To: git; +Cc: Jonathan Tan

A subsequent commit will need part, but not all, of the functionality in
add_haves(), so move some of its functionality to its sole caller
send_fetch_request().

Signed-off-by: Jonathan Tan <jonathantanmy@google.com>
---
 fetch-pack.c | 28 ++++++++++++----------------
 1 file changed, 12 insertions(+), 16 deletions(-)

diff --git a/fetch-pack.c b/fetch-pack.c
index 9f3901cdba..128ad47d2a 100644
--- a/fetch-pack.c
+++ b/fetch-pack.c
@@ -1195,11 +1195,9 @@ static void add_common(struct strbuf *req_buf, struct oidset *common)
 }
 
 static int add_haves(struct fetch_negotiator *negotiator,
-		     int seen_ack,
 		     struct strbuf *req_buf,
-		     int *haves_to_send, int *in_vain)
+		     int *haves_to_send)
 {
-	int ret = 0;
 	int haves_added = 0;
 	const struct object_id *oid;
 
@@ -1209,17 +1207,10 @@ static int add_haves(struct fetch_negotiator *negotiator,
 			break;
 	}
 
-	*in_vain += haves_added;
-	if (!haves_added || (seen_ack && *in_vain >= MAX_IN_VAIN)) {
-		/* Send Done */
-		packet_buf_write(req_buf, "done\n");
-		ret = 1;
-	}
-
 	/* Increase haves to send on next round */
 	*haves_to_send = next_flush(1, *haves_to_send);
 
-	return ret;
+	return haves_added;
 }
 
 static int send_fetch_request(struct fetch_negotiator *negotiator, int fd_out,
@@ -1228,7 +1219,8 @@ static int send_fetch_request(struct fetch_negotiator *negotiator, int fd_out,
 			      int *haves_to_send, int *in_vain,
 			      int sideband_all, int seen_ack)
 {
-	int ret = 0;
+	int haves_added;
+	int done_sent = 0;
 	const char *hash_name;
 	struct strbuf req_buf = STRBUF_INIT;
 
@@ -1312,9 +1304,13 @@ static int send_fetch_request(struct fetch_negotiator *negotiator, int fd_out,
 	/* Add all of the common commits we've found in previous rounds */
 	add_common(&req_buf, common);
 
-	/* Add initial haves */
-	ret = add_haves(negotiator, seen_ack, &req_buf,
-			haves_to_send, in_vain);
+	haves_added = add_haves(negotiator, &req_buf, haves_to_send);
+	*in_vain += haves_added;
+	if (!haves_added || (seen_ack && *in_vain >= MAX_IN_VAIN)) {
+		/* Send Done */
+		packet_buf_write(&req_buf, "done\n");
+		done_sent = 1;
+	}
 
 	/* Send request */
 	packet_buf_flush(&req_buf);
@@ -1322,7 +1318,7 @@ static int send_fetch_request(struct fetch_negotiator *negotiator, int fd_out,
 		die_errno(_("unable to write request to remote"));
 
 	strbuf_release(&req_buf);
-	return ret;
+	return done_sent;
 }
 
 /*
-- 
2.31.1.295.g9ea45b61b8-goog


^ permalink raw reply	[flat|nested] 33+ messages in thread

* [PATCH 4/6] fetch-pack: refactor command and capability write
  2021-04-09  1:09 [PATCH 0/6] Push negotiation Jonathan Tan
                   ` (2 preceding siblings ...)
  2021-04-09  1:10 ` [PATCH 3/6] fetch-pack: refactor add_haves() Jonathan Tan
@ 2021-04-09  1:10 ` Jonathan Tan
  2021-04-09  5:27   ` Junio C Hamano
  2021-04-09  1:10 ` [PATCH 5/6] fetch: teach independent negotiation (no packfile) Jonathan Tan
                   ` (3 subsequent siblings)
  7 siblings, 1 reply; 33+ messages in thread
From: Jonathan Tan @ 2021-04-09  1:10 UTC (permalink / raw)
  To: git; +Cc: Jonathan Tan

A subsequent commit will need this functionality independent of the rest
of send_fetch_request(), so put this into its own function.

Signed-off-by: Jonathan Tan <jonathantanmy@google.com>
---
 fetch-pack.c | 41 ++++++++++++++++++++++++-----------------
 1 file changed, 24 insertions(+), 17 deletions(-)

diff --git a/fetch-pack.c b/fetch-pack.c
index 128ad47d2a..512fe5450d 100644
--- a/fetch-pack.c
+++ b/fetch-pack.c
@@ -1213,29 +1213,23 @@ static int add_haves(struct fetch_negotiator *negotiator,
 	return haves_added;
 }
 
-static int send_fetch_request(struct fetch_negotiator *negotiator, int fd_out,
-			      struct fetch_pack_args *args,
-			      const struct ref *wants, struct oidset *common,
-			      int *haves_to_send, int *in_vain,
-			      int sideband_all, int seen_ack)
+static void write_fetch_command_and_capabilities(struct strbuf *req_buf,
+						 const struct string_list *server_options)
 {
-	int haves_added;
-	int done_sent = 0;
 	const char *hash_name;
-	struct strbuf req_buf = STRBUF_INIT;
 
 	if (server_supports_v2("fetch", 1))
-		packet_buf_write(&req_buf, "command=fetch");
+		packet_buf_write(req_buf, "command=fetch");
 	if (server_supports_v2("agent", 0))
-		packet_buf_write(&req_buf, "agent=%s", git_user_agent_sanitized());
+		packet_buf_write(req_buf, "agent=%s", git_user_agent_sanitized());
 	if (advertise_sid && server_supports_v2("session-id", 0))
-		packet_buf_write(&req_buf, "session-id=%s", trace2_session_id());
-	if (args->server_options && args->server_options->nr &&
+		packet_buf_write(req_buf, "session-id=%s", trace2_session_id());
+	if (server_options && server_options->nr &&
 	    server_supports_v2("server-option", 1)) {
 		int i;
-		for (i = 0; i < args->server_options->nr; i++)
-			packet_buf_write(&req_buf, "server-option=%s",
-					 args->server_options->items[i].string);
+		for (i = 0; i < server_options->nr; i++)
+			packet_buf_write(req_buf, "server-option=%s",
+					 server_options->items[i].string);
 	}
 
 	if (server_feature_v2("object-format", &hash_name)) {
@@ -1243,13 +1237,26 @@ static int send_fetch_request(struct fetch_negotiator *negotiator, int fd_out,
 		if (hash_algo_by_ptr(the_hash_algo) != hash_algo)
 			die(_("mismatched algorithms: client %s; server %s"),
 			    the_hash_algo->name, hash_name);
-		packet_buf_write(&req_buf, "object-format=%s", the_hash_algo->name);
+		packet_buf_write(req_buf, "object-format=%s", the_hash_algo->name);
 	} else if (hash_algo_by_ptr(the_hash_algo) != GIT_HASH_SHA1) {
 		die(_("the server does not support algorithm '%s'"),
 		    the_hash_algo->name);
 	}
+	packet_buf_delim(req_buf);
+}
+
+static int send_fetch_request(struct fetch_negotiator *negotiator, int fd_out,
+			      struct fetch_pack_args *args,
+			      const struct ref *wants, struct oidset *common,
+			      int *haves_to_send, int *in_vain,
+			      int sideband_all, int seen_ack)
+{
+	int haves_added;
+	int done_sent = 0;
+	struct strbuf req_buf = STRBUF_INIT;
+
+	write_fetch_command_and_capabilities(&req_buf, args->server_options);
 
-	packet_buf_delim(&req_buf);
 	if (args->use_thin_pack)
 		packet_buf_write(&req_buf, "thin-pack");
 	if (args->no_progress)
-- 
2.31.1.295.g9ea45b61b8-goog


^ permalink raw reply	[flat|nested] 33+ messages in thread

* [PATCH 5/6] fetch: teach independent negotiation (no packfile)
  2021-04-09  1:09 [PATCH 0/6] Push negotiation Jonathan Tan
                   ` (3 preceding siblings ...)
  2021-04-09  1:10 ` [PATCH 4/6] fetch-pack: refactor command and capability write Jonathan Tan
@ 2021-04-09  1:10 ` Jonathan Tan
  2021-04-09  5:41   ` Junio C Hamano
  2021-05-03 15:25   ` Derrick Stolee
  2021-04-09  1:10 ` [PATCH 6/6] send-pack: support push negotiation Jonathan Tan
                   ` (2 subsequent siblings)
  7 siblings, 2 replies; 33+ messages in thread
From: Jonathan Tan @ 2021-04-09  1:10 UTC (permalink / raw)
  To: git; +Cc: Jonathan Tan

Currently, the packfile negotiation step within a Git fetch cannot be
done independent of sending the packfile, even though there is at least
one application wherein this is useful. Therefore, make it possible for
this negotiation step to be done independently. A subsequent commit will
use this for one such application - push negotiation.

This feature is for protocol v2 only. (An implementation for protocol v0
would require a separate implementation in the fetch, transport, and
transport helper code.)

In the protocol, the main hindrance towards independent negotiation is
that the server can unilaterally decide to send the packfile. This is
solved by a "wait-for-done" argument: the server will then wait for the
client to say "done". In practice, the client will never say it; instead
it will cease requests once it is satisfied.

In the client, the main change lies in the transport and transport
helper code. fetch_refs_via_pack() performs everything needed - protocol
version and capability checks, and the negotiation itself.

There are 2 code paths that do not go through fetch_refs_via_pack() that
needed to be individually excluded: the bundle transport (excluded
through requiring smart_options, which the bundle transport doesn't
support) and transport helpers that do not support takeover.
Fortunately, none of these support protocol v2.

Signed-off-by: Jonathan Tan <jonathantanmy@google.com>
---
 Documentation/technical/protocol-v2.txt |  8 +++
 builtin/fetch.c                         | 27 +++++++-
 fetch-pack.c                            | 89 +++++++++++++++++++++++--
 fetch-pack.h                            | 11 +++
 object.h                                |  2 +-
 t/t5701-git-serve.sh                    |  2 +-
 t/t5702-protocol-v2.sh                  | 89 +++++++++++++++++++++++++
 transport-helper.c                      | 10 +++
 transport.c                             | 30 +++++++--
 transport.h                             |  6 ++
 upload-pack.c                           | 18 +++--
 11 files changed, 275 insertions(+), 17 deletions(-)

diff --git a/Documentation/technical/protocol-v2.txt b/Documentation/technical/protocol-v2.txt
index a7c806a73e..0b371d8de4 100644
--- a/Documentation/technical/protocol-v2.txt
+++ b/Documentation/technical/protocol-v2.txt
@@ -346,6 +346,14 @@ explained below.
 	client should download from all given URIs. Currently, the
 	protocols supported are "http" and "https".
 
+If the 'wait-for-done' feature is advertised, the following argument
+can be included in the client's request.
+
+    wait-for-done
+	Indicates to the server that it should never send "ready", but
+	should wait for the client to say "done" before sending the
+	packfile.
+
 The response of `fetch` is broken into a number of sections separated by
 delimiter packets (0001), with each section beginning with its section
 header. Most sections are sent only when the packfile is sent.
diff --git a/builtin/fetch.c b/builtin/fetch.c
index 0b90de87c7..597973848a 100644
--- a/builtin/fetch.c
+++ b/builtin/fetch.c
@@ -82,6 +82,7 @@ static struct string_list server_options = STRING_LIST_INIT_DUP;
 static struct string_list negotiation_tip = STRING_LIST_INIT_NODUP;
 static int fetch_write_commit_graph = -1;
 static int stdin_refspecs = 0;
+static int negotiate_only;
 
 static int git_fetch_config(const char *k, const char *v, void *cb)
 {
@@ -202,6 +203,8 @@ static struct option builtin_fetch_options[] = {
 			TRANSPORT_FAMILY_IPV6),
 	OPT_STRING_LIST(0, "negotiation-tip", &negotiation_tip, N_("revision"),
 			N_("report that we have only objects reachable from this object")),
+	OPT_BOOL(0, "negotiate-only", &negotiate_only,
+		 N_("do not fetch a packfile; instead, print ancestors of negotiation tips")),
 	OPT_PARSE_LIST_OBJECTS_FILTER(&filter_options),
 	OPT_BOOL(0, "auto-maintenance", &enable_auto_gc,
 		 N_("run 'maintenance --auto' after fetching")),
@@ -1986,7 +1989,29 @@ int cmd_fetch(int argc, const char **argv, const char *prefix)
 		}
 	}
 
-	if (remote) {
+	if (negotiate_only) {
+		struct oidset acked_commits = OIDSET_INIT;
+		struct oidset_iter iter;
+		const struct object_id *oid;
+
+		if (!remote)
+			die(_("Must supply remote when using --negotiate-only"));
+		gtransport = prepare_transport(remote, 1);
+		if (gtransport->smart_options) {
+			gtransport->smart_options->acked_commits = &acked_commits;
+		} else {
+			warning(_("Protocol does not support --negotiate-only, exiting."));
+			return 1;
+		}
+		if (server_options.nr)
+			gtransport->server_options = &server_options;
+		result = transport_fetch_refs(gtransport, NULL);
+
+		oidset_iter_init(&acked_commits, &iter);
+		while ((oid = oidset_iter_next(&iter)))
+			printf("%s\n", oid_to_hex(oid));
+		oidset_clear(&acked_commits);
+	} else if (remote) {
 		if (filter_options.choice || has_promisor_remote())
 			fetch_one_setup_partial(remote);
 		result = fetch_one(remote, argc, argv, prune_tags_ok, stdin_refspecs);
diff --git a/fetch-pack.c b/fetch-pack.c
index 512fe5450d..63054e2fc8 100644
--- a/fetch-pack.c
+++ b/fetch-pack.c
@@ -23,6 +23,7 @@
 #include "fetch-negotiator.h"
 #include "fsck.h"
 #include "shallow.h"
+#include "commit-reach.h"
 
 static int transfer_unpack_limit = -1;
 static int fetch_unpack_limit = -1;
@@ -45,6 +46,8 @@ static struct string_list uri_protocols = STRING_LIST_INIT_DUP;
 /* Remember to update object flag allocation in object.h */
 #define COMPLETE	(1U << 0)
 #define ALTERNATE	(1U << 1)
+#define COMMON		(1U << 6)
+#define REACH_SCRATCH	(1U << 7)
 
 /*
  * After sending this many "have"s if we do not get any new ACK , we
@@ -1523,10 +1526,10 @@ enum fetch_state {
 	FETCH_DONE,
 };
 
-static void do_check_stateless_delimiter(const struct fetch_pack_args *args,
+static void do_check_stateless_delimiter(int stateless_rpc,
 					 struct packet_reader *reader)
 {
-	check_stateless_delimiter(args->stateless_rpc, reader,
+	check_stateless_delimiter(stateless_rpc, reader,
 				  _("git fetch-pack: expected response end packet"));
 }
 
@@ -1622,7 +1625,7 @@ static struct ref *do_fetch_pack_v2(struct fetch_pack_args *args,
 				 */
 				state = FETCH_GET_PACK;
 			} else {
-				do_check_stateless_delimiter(args, &reader);
+				do_check_stateless_delimiter(args->stateless_rpc, &reader);
 				state = FETCH_SEND_REQUEST;
 			}
 			break;
@@ -1645,7 +1648,7 @@ static struct ref *do_fetch_pack_v2(struct fetch_pack_args *args,
 				     packfile_uris.nr ? &index_pack_args : NULL,
 				     sought, nr_sought, &fsck_options.gitmodules_found))
 				die(_("git fetch-pack: fetch failed."));
-			do_check_stateless_delimiter(args, &reader);
+			do_check_stateless_delimiter(args->stateless_rpc, &reader);
 
 			state = FETCH_DONE;
 			break;
@@ -1962,6 +1965,84 @@ struct ref *fetch_pack(struct fetch_pack_args *args,
 	return ref_cpy;
 }
 
+static int add_to_object_array(const struct object_id *oid, void *data)
+{
+	struct object_array *a = data;
+
+	add_object_array(parse_object(the_repository, oid), "", a);
+	return 0;
+}
+
+void negotiate_using_fetch(const struct oid_array *negotiation_tips,
+			   const struct string_list *server_options,
+			   int stateless_rpc,
+			   int fd[],
+			   struct oidset *acked_commits)
+{
+	struct fetch_negotiator negotiator;
+	struct packet_reader reader;
+	struct object_array nt_object_array = OBJECT_ARRAY_INIT;
+	struct strbuf req_buf = STRBUF_INIT;
+	int haves_to_send = INITIAL_FLUSH;
+	int in_vain = 0;
+	int seen_ack = 0;
+	int last_iteration = 0;
+
+	fetch_negotiator_init(the_repository, &negotiator);
+	mark_tips(&negotiator, negotiation_tips);
+
+	packet_reader_init(&reader, fd[0], NULL, 0,
+			   PACKET_READ_CHOMP_NEWLINE |
+			   PACKET_READ_DIE_ON_ERR_PACKET);
+
+	oid_array_for_each((struct oid_array *) negotiation_tips,
+			   add_to_object_array,
+			   &nt_object_array);
+
+	while (!last_iteration) {
+		int haves_added;
+		struct object_id common_oid;
+		int received_ready = 0;
+
+		strbuf_reset(&req_buf);
+		write_fetch_command_and_capabilities(&req_buf, server_options);
+
+		packet_buf_write(&req_buf, "wait-for-done");
+
+		haves_added = add_haves(&negotiator, &req_buf, &haves_to_send);
+		in_vain += haves_added;
+		if (!haves_added || (seen_ack && in_vain >= MAX_IN_VAIN))
+			last_iteration = 1;
+
+		/* Send request */
+		packet_buf_flush(&req_buf);
+		if (write_in_full(fd[1], req_buf.buf, req_buf.len) < 0)
+			die_errno(_("unable to write request to remote"));
+
+		/* Process ACKs/NAKs */
+		process_section_header(&reader, "acknowledgments", 0);
+		while (process_ack(&negotiator, &reader, &common_oid,
+				   &received_ready)) {
+			struct commit *commit = lookup_commit(the_repository,
+							      &common_oid);
+			if (commit)
+				commit->object.flags |= COMMON;
+			in_vain = 0;
+			seen_ack = 1;
+			oidset_insert(acked_commits, &common_oid);
+		}
+		if (received_ready)
+			die(_("unexpected 'ready' from remote"));
+		else
+			do_check_stateless_delimiter(stateless_rpc, &reader);
+		if (can_all_from_reach_with_flag(&nt_object_array, COMMON,
+						 REACH_SCRATCH, 0,
+						 GENERATION_NUMBER_ZERO))
+			last_iteration = 1;
+	}
+	strbuf_release(&req_buf);
+}
+
 int report_unmatched_refs(struct ref **sought, int nr_sought)
 {
 	int i, ret = 0;
diff --git a/fetch-pack.h b/fetch-pack.h
index f114d72775..7c8f49aca7 100644
--- a/fetch-pack.h
+++ b/fetch-pack.h
@@ -5,6 +5,7 @@
 #include "run-command.h"
 #include "protocol.h"
 #include "list-objects-filter-options.h"
+#include "oidset.h"
 
 struct oid_array;
 
@@ -81,6 +82,16 @@ struct ref *fetch_pack(struct fetch_pack_args *args,
 		       struct string_list *pack_lockfiles,
 		       enum protocol_version version);
 
+/*
+ * Execute the --negotiate-only mode of "git fetch", adding all known common
+ * commits to acked_commits.
+ */
+void negotiate_using_fetch(const struct oid_array *negotiation_tips,
+			   const struct string_list *server_options,
+			   int stateless_rpc,
+			   int fd[],
+			   struct oidset *acked_commits);
+
 /*
  * Print an appropriate error message for each sought ref that wasn't
  * matched.  Return 0 if all sought refs were matched, otherwise 1.
diff --git a/object.h b/object.h
index 59daadce21..4806fa8e66 100644
--- a/object.h
+++ b/object.h
@@ -60,7 +60,7 @@ struct object_array {
 /*
  * object flag allocation:
  * revision.h:               0---------10         15             23------26
- * fetch-pack.c:             01
+ * fetch-pack.c:             01    67
  * negotiator/default.c:       2--5
  * walker.c:                 0-2
  * upload-pack.c:                4       11-----14  16-----19
diff --git a/t/t5701-git-serve.sh b/t/t5701-git-serve.sh
index 509f379d49..f03bb04803 100755
--- a/t/t5701-git-serve.sh
+++ b/t/t5701-git-serve.sh
@@ -16,7 +16,7 @@ test_expect_success 'test capability advertisement' '
 	version 2
 	agent=git/$(git version | cut -d" " -f3)
 	ls-refs=unborn
-	fetch=shallow
+	fetch=shallow wait-for-done
 	server-option
 	object-format=$(test_oid algo)
 	0000
diff --git a/t/t5702-protocol-v2.sh b/t/t5702-protocol-v2.sh
index 2e1243ca40..5d91f067d0 100755
--- a/t/t5702-protocol-v2.sh
+++ b/t/t5702-protocol-v2.sh
@@ -585,6 +585,49 @@ test_expect_success 'deepen-relative' '
 	test_cmp expected actual
 '
 
+setup_negotiate_only () {
+	SERVER="$1"
+	URI="$2"
+
+	rm -rf "$SERVER" client
+
+	git init "$SERVER"
+	test_commit -C "$SERVER" one
+	test_commit -C "$SERVER" two
+
+	git clone "$URI" client
+	test_commit -C client three
+}
+
+test_expect_success 'file:// --negotiate-only' '
+	SERVER="server" &&
+	URI="file://$(pwd)/server" &&
+
+	setup_negotiate_only "$SERVER" "$URI" &&
+
+	git -C client fetch \
+		--no-tags \
+		--negotiate-only \
+		--negotiation-tip=$(git -C client rev-parse HEAD) \
+		origin >out &&
+	COMMON=$(git -C "$SERVER" rev-parse two) &&
+	grep "$COMMON" out
+'
+
+test_expect_success 'file:// --negotiate-only with protocol v0' '
+	SERVER="server" &&
+	URI="file://$(pwd)/server" &&
+
+	setup_negotiate_only "$SERVER" "$URI" &&
+
+	test_must_fail git -c protocol.version=0 -C client fetch \
+		--no-tags \
+		--negotiate-only \
+		--negotiation-tip=$(git -C client rev-parse HEAD) \
+		origin 2>err &&
+	test_i18ngrep "negotiate-only requires protocol v2" err
+'
+
 # Test protocol v2 with 'http://' transport
 #
 . "$TEST_DIRECTORY"/lib-httpd.sh
@@ -1035,6 +1078,52 @@ test_expect_success 'packfile-uri with transfer.fsckobjects fails when .gitmodul
 	test_i18ngrep "disallowed submodule name" err
 '
 
+test_expect_success 'http:// --negotiate-only' '
+	SERVER="$HTTPD_DOCUMENT_ROOT_PATH/server" &&
+	URI="$HTTPD_URL/smart/server" &&
+
+	setup_negotiate_only "$SERVER" "$URI" &&
+
+	git -C client fetch \
+		--no-tags \
+		--negotiate-only \
+		--negotiation-tip=$(git -C client rev-parse HEAD) \
+		origin >out &&
+	COMMON=$(git -C "$SERVER" rev-parse two) &&
+	grep "$COMMON" out
+'
+
+test_expect_success 'http:// --negotiate-only without wait-for-done support' '
+	SERVER="server" &&
+	URI="$HTTPD_URL/one_time_perl/server" &&
+
+	setup_negotiate_only "$SERVER" "$URI" &&
+
+	echo "s/ wait-for-done/ xxxx-xxx-xxxx/" \
+		>"$HTTPD_ROOT_PATH/one-time-perl" &&
+
+	test_must_fail git -C client fetch \
+		--no-tags \
+		--negotiate-only \
+		--negotiation-tip=$(git -C client rev-parse HEAD) \
+		origin 2>err &&
+	test_i18ngrep "server does not support wait-for-done" err
+'
+
+test_expect_success 'http:// --negotiate-only with protocol v0' '
+	SERVER="$HTTPD_DOCUMENT_ROOT_PATH/server" &&
+	URI="$HTTPD_URL/smart/server" &&
+
+	setup_negotiate_only "$SERVER" "$URI" &&
+
+	test_must_fail git -c protocol.version=0 -C client fetch \
+		--no-tags \
+		--negotiate-only \
+		--negotiation-tip=$(git -C client rev-parse HEAD) \
+		origin 2>err &&
+	test_i18ngrep "negotiate-only requires protocol v2" err
+'
+
 # DO NOT add non-httpd-specific tests here, because the last part of this
 # test script is only executed when httpd is available and enabled.
 
diff --git a/transport-helper.c b/transport-helper.c
index 4cd76366fa..4be035edb8 100644
--- a/transport-helper.c
+++ b/transport-helper.c
@@ -684,6 +684,16 @@ static int fetch(struct transport *transport,
 		return transport->vtable->fetch(transport, nr_heads, to_fetch);
 	}
 
+	/*
+	 * If we reach here, then the server, the client, and/or the transport
+	 * helper does not support protocol v2. --negotiate-only requires
+	 * protocol v2.
+	 */
+	if (data->transport_options.acked_commits) {
+		warning(_("--negotiate-only requires protocol v2"));
+		return -1;
+	}
+
 	if (!data->get_refs_list_called)
 		get_refs_list_using_list(transport, 0);
 
diff --git a/transport.c b/transport.c
index ef66e73090..80caeaa72f 100644
--- a/transport.c
+++ b/transport.c
@@ -392,16 +392,29 @@ static int fetch_refs_via_pack(struct transport *transport,
 	else if (data->version <= protocol_v1)
 		die_if_server_options(transport);
 
+	if (data->options.acked_commits) {
+		if (data->version < protocol_v2) {
+			warning(_("--negotiate-only requires protocol v2"));
+			ret = -1;
+		} else if (!server_supports_feature("fetch", "wait-for-done", 0)) {
+			warning(_("server does not support wait-for-done"));
+			ret = -1;
+		} else {
+			negotiate_using_fetch(data->options.negotiation_tips,
+					      transport->server_options,
+					      transport->stateless_rpc,
+					      data->fd,
+					      data->options.acked_commits);
+			ret = 0;
+		}
+		goto cleanup;
+	}
+
 	refs = fetch_pack(&args, data->fd,
 			  refs_tmp ? refs_tmp : transport->remote_refs,
 			  to_fetch, nr_heads, &data->shallow,
 			  &transport->pack_lockfiles, data->version);
 
-	close(data->fd[0]);
-	close(data->fd[1]);
-	if (finish_connect(data->conn))
-		ret = -1;
-	data->conn = NULL;
 	data->got_remote_heads = 0;
 	data->options.self_contained_and_connected =
 		args.self_contained_and_connected;
@@ -412,6 +425,13 @@ static int fetch_refs_via_pack(struct transport *transport,
 	if (report_unmatched_refs(to_fetch, nr_heads))
 		ret = -1;
 
+cleanup:
+	close(data->fd[0]);
+	close(data->fd[1]);
+	if (finish_connect(data->conn))
+		ret = -1;
+	data->conn = NULL;
+
 	free_refs(refs_tmp);
 	free_refs(refs);
 	return ret;
diff --git a/transport.h b/transport.h
index 4d5db0a7f2..b8b3d42e62 100644
--- a/transport.h
+++ b/transport.h
@@ -47,6 +47,12 @@ struct git_transport_options {
 	 * transport_set_option().
 	 */
 	struct oid_array *negotiation_tips;
+
+	/*
+	 * If set, whenever transport_fetch_refs() is called, add known common
+	 * commits to this oidset instead of fetching any packfiles.
+	 */
+	struct oidset *acked_commits;
 };
 
 enum transport_family {
diff --git a/upload-pack.c b/upload-pack.c
index e19583ae0f..b432ef0119 100644
--- a/upload-pack.c
+++ b/upload-pack.c
@@ -103,6 +103,7 @@ struct upload_pack_data {
 	unsigned use_ofs_delta : 1;
 	unsigned no_progress : 1;
 	unsigned use_include_tag : 1;
+	unsigned wait_for_done : 1;
 	unsigned allow_filter : 1;
 	unsigned allow_filter_fallback : 1;
 	unsigned long tree_filter_max_depth;
@@ -1496,6 +1497,10 @@ static void process_args(struct packet_reader *request,
 			data->done = 1;
 			continue;
 		}
+		if (!strcmp(arg, "wait-for-done")) {
+			data->wait_for_done = 1;
+			continue;
+		}
 
 		/* Shallow related arguments */
 		if (process_shallow(arg, &data->shallows))
@@ -1578,7 +1583,7 @@ static int send_acks(struct upload_pack_data *data, struct oid_array *acks)
 				    oid_to_hex(&acks->oid[i]));
 	}
 
-	if (ok_to_give_up(data)) {
+	if (!data->wait_for_done && ok_to_give_up(data)) {
 		/* Send Ready */
 		packet_writer_write(&data->writer, "ready\n");
 		return 1;
@@ -1668,10 +1673,13 @@ int upload_pack_v2(struct repository *r, struct strvec *keys,
 		case FETCH_PROCESS_ARGS:
 			process_args(request, &data);
 
-			if (!data.want_obj.nr) {
+			if (!data.want_obj.nr && !data.wait_for_done) {
 				/*
-				 * Request didn't contain any 'want' lines,
-				 * guess they didn't want anything.
+				 * Request didn't contain any 'want' lines (and
+				 * the request does not contain
+				 * "wait-for-done", in which it is reasonable
+				 * to just send 'have's without 'want's); guess
+				 * they didn't want anything.
 				 */
 				state = FETCH_DONE;
 			} else if (data.haves.nr) {
@@ -1723,7 +1731,7 @@ int upload_pack_advertise(struct repository *r,
 		int allow_sideband_all_value;
 		char *str = NULL;
 
-		strbuf_addstr(value, "shallow");
+		strbuf_addstr(value, "shallow wait-for-done");
 
 		if (!repo_config_get_bool(the_repository,
 					 "uploadpack.allowfilter",
-- 
2.31.1.295.g9ea45b61b8-goog


^ permalink raw reply	[flat|nested] 33+ messages in thread

* [PATCH 6/6] send-pack: support push negotiation
  2021-04-09  1:09 [PATCH 0/6] Push negotiation Jonathan Tan
                   ` (4 preceding siblings ...)
  2021-04-09  1:10 ` [PATCH 5/6] fetch: teach independent negotiation (no packfile) Jonathan Tan
@ 2021-04-09  1:10 ` Jonathan Tan
  2021-05-03 15:35   ` Derrick Stolee
  2021-04-30  5:42 ` [PATCH 0/6] Push negotiation Junio C Hamano
  2021-05-04 21:15 ` [PATCH v2 0/5] " Jonathan Tan
  7 siblings, 1 reply; 33+ messages in thread
From: Jonathan Tan @ 2021-04-09  1:10 UTC (permalink / raw)
  To: git; +Cc: Jonathan Tan

Teach Git the push.negotiate config variable.

Signed-off-by: Jonathan Tan <jonathantanmy@google.com>
---
 Documentation/config/push.txt |  7 ++++
 send-pack.c                   | 61 ++++++++++++++++++++++++++++++++---
 t/t5516-fetch-push.sh         | 35 ++++++++++++++++++++
 3 files changed, 99 insertions(+), 4 deletions(-)

diff --git a/Documentation/config/push.txt b/Documentation/config/push.txt
index 21b256e0a4..f2667b2689 100644
--- a/Documentation/config/push.txt
+++ b/Documentation/config/push.txt
@@ -120,3 +120,10 @@ push.useForceIfIncludes::
 	`--force-if-includes` as an option to linkgit:git-push[1]
 	in the command line. Adding `--no-force-if-includes` at the
 	time of push overrides this configuration setting.
+
+push.negotiate::
+	If set to "true", attempt to reduce the size of the packfile
+	sent by rounds of negotiation in which the client and the
+	server attempt to find commits in common. If "false", Git will
+	rely solely on the server's ref advertisement to find commits
+	in common.
diff --git a/send-pack.c b/send-pack.c
index 5f215b13c7..9cb9f71650 100644
--- a/send-pack.c
+++ b/send-pack.c
@@ -56,7 +56,9 @@ static void feed_object(const struct object_id *oid, FILE *fh, int negative)
 /*
  * Make a pack stream and spit it out into file descriptor fd
  */
-static int pack_objects(int fd, struct ref *refs, struct oid_array *extra, struct send_pack_args *args)
+static int pack_objects(int fd, struct ref *refs, struct oid_array *advertised,
+			struct oid_array *negotiated,
+			struct send_pack_args *args)
 {
 	/*
 	 * The child becomes pack-objects --revs; we feed
@@ -94,8 +96,10 @@ static int pack_objects(int fd, struct ref *refs, struct oid_array *extra, struc
 	 * parameters by writing to the pipe.
 	 */
 	po_in = xfdopen(po.in, "w");
-	for (i = 0; i < extra->nr; i++)
-		feed_object(&extra->oid[i], po_in, 1);
+	for (i = 0; i < advertised->nr; i++)
+		feed_object(&advertised->oid[i], po_in, 1);
+	for (i = 0; i < negotiated->nr; i++)
+		feed_object(&negotiated->oid[i], po_in, 1);
 
 	while (refs) {
 		if (!is_null_oid(&refs->old_oid))
@@ -409,11 +413,55 @@ static void reject_invalid_nonce(const char *nonce, int len)
 	}
 }
 
+static void get_commons_through_negotiation(const char *url,
+					    const struct ref *remote_refs,
+					    struct oid_array *commons)
+{
+	struct child_process child = CHILD_PROCESS_INIT;
+	const struct ref *ref;
+	int len = the_hash_algo->hexsz + 1; /* hash + NL */
+
+	child.git_cmd = 1;
+	child.no_stdin = 1;
+	child.out = -1;
+	strvec_pushl(&child.args, "fetch", "--negotiate-only", NULL);
+	for (ref = remote_refs; ref; ref = ref->next)
+		strvec_pushf(&child.args, "--negotiation-tip=%s", oid_to_hex(&ref->new_oid));
+	strvec_push(&child.args, url);
+
+	if (start_command(&child))
+		die(_("send-pack: unable to fork off fetch subprocess"));
+
+	do {
+		char hex_hash[GIT_MAX_HEXSZ + 1];
+		int read_len = read_in_full(child.out, hex_hash, len);
+		struct object_id oid;
+		const char *end;
+
+		if (!read_len)
+			break;
+		if (read_len != len)
+			die("invalid length read %d", read_len);
+		if (parse_oid_hex(hex_hash, &oid, &end) || *end != '\n')
+			die("invalid hash");
+		oid_array_append(commons, &oid);
+	} while (1);
+
+	if (finish_command(&child)) {
+		/*
+		 * The information that push negotiation provides is useful but
+		 * not mandatory.
+		 */
+		warning(_("push negotiation failed; proceeding anyway with push"));
+	}
+}
+
 int send_pack(struct send_pack_args *args,
 	      int fd[], struct child_process *conn,
 	      struct ref *remote_refs,
 	      struct oid_array *extra_have)
 {
+	struct oid_array commons = OID_ARRAY_INIT;
 	int in = fd[0];
 	int out = fd[1];
 	struct strbuf req_buf = STRBUF_INIT;
@@ -426,6 +474,7 @@ int send_pack(struct send_pack_args *args,
 	int quiet_supported = 0;
 	int agent_supported = 0;
 	int advertise_sid = 0;
+	int push_negotiate = 0;
 	int use_atomic = 0;
 	int atomic_supported = 0;
 	int use_push_options = 0;
@@ -437,6 +486,10 @@ int send_pack(struct send_pack_args *args,
 	const char *push_cert_nonce = NULL;
 	struct packet_reader reader;
 
+	git_config_get_bool("push.negotiate", &push_negotiate);
+	if (push_negotiate)
+		get_commons_through_negotiation(args->url, remote_refs, &commons);
+
 	git_config_get_bool("transfer.advertisesid", &advertise_sid);
 
 	/* Does the other end support the reporting? */
@@ -625,7 +678,7 @@ int send_pack(struct send_pack_args *args,
 			   PACKET_READ_DIE_ON_ERR_PACKET);
 
 	if (need_pack_data && cmds_sent) {
-		if (pack_objects(out, remote_refs, extra_have, args) < 0) {
+		if (pack_objects(out, remote_refs, extra_have, &commons, args) < 0) {
 			if (args->stateless_rpc)
 				close(out);
 			if (git_connection_is_socket(conn))
diff --git a/t/t5516-fetch-push.sh b/t/t5516-fetch-push.sh
index f11742ed59..62fb9074a2 100755
--- a/t/t5516-fetch-push.sh
+++ b/t/t5516-fetch-push.sh
@@ -191,6 +191,41 @@ test_expect_success 'fetch with pushInsteadOf (should not rewrite)' '
 	)
 '
 
+grep_wrote () {
+	object_count=$1
+	file_name=$2
+	grep 'write_pack_file/wrote.*"value":"'$1'"' $2
+}
+
+test_expect_success 'push with negotiation' '
+	# Without negotiation
+	mk_empty testrepo &&
+	git push testrepo $the_first_commit:refs/remotes/origin/first_commit &&
+	git -C testrepo config receive.hideRefs refs/remotes/origin/first_commit &&
+	echo now pushing without negotiation &&
+	GIT_TRACE2_EVENT="$(pwd)/event" git push testrepo refs/heads/main:refs/remotes/origin/main &&
+	grep_wrote 5 event && # 2 commits, 2 trees, 1 blob
+
+	# Same commands, but with negotiation
+	rm event &&
+	mk_empty testrepo &&
+	git push testrepo $the_first_commit:refs/remotes/origin/first_commit &&
+	git -C testrepo config receive.hideRefs refs/remotes/origin/first_commit &&
+	GIT_TRACE2_EVENT="$(pwd)/event" git -c push.negotiate=1 push testrepo refs/heads/main:refs/remotes/origin/main &&
+	grep_wrote 2 event # 1 commit, 1 tree
+'
+
+test_expect_success 'push with negotiation proceeds anyway even if negotiation fails' '
+	rm event &&
+	mk_empty testrepo &&
+	git push testrepo $the_first_commit:refs/remotes/origin/first_commit &&
+	git -C testrepo config receive.hideRefs refs/remotes/origin/first_commit &&
+	GIT_TRACE_PACKET="$(pwd)/trace" GIT_TEST_PROTOCOL_VERSION=0 GIT_TRACE2_EVENT="$(pwd)/event" \
+		git -c push.negotiate=1 push testrepo refs/heads/main:refs/remotes/origin/main 2>err &&
+	grep_wrote 5 event && # 2 commits, 2 trees, 1 blob
+	test_i18ngrep "push negotiation failed" err
+'
+
 test_expect_success 'push without wildcard' '
 	mk_empty testrepo &&
 
-- 
2.31.1.295.g9ea45b61b8-goog


^ permalink raw reply	[flat|nested] 33+ messages in thread

* Re: [PATCH 1/6] fetch-pack: buffer object-format with other args
  2021-04-09  1:09 ` [PATCH 1/6] fetch-pack: buffer object-format with other args Jonathan Tan
@ 2021-04-09  4:49   ` Junio C Hamano
  2021-04-09 16:24     ` Jonathan Tan
  0 siblings, 1 reply; 33+ messages in thread
From: Junio C Hamano @ 2021-04-09  4:49 UTC (permalink / raw)
  To: Jonathan Tan; +Cc: git

Jonathan Tan <jonathantanmy@google.com> writes:

> In send_fetch_request(), "object-format" is written directly to the file
> descriptor, as opposed to the other arguments, which are buffered.
> Buffer "object-format" as well. "object-format" must be buffered; in
> particular, it must appear after "command=fetch" in the request.
>
> This divergence was introduced in 4b831208bb ("fetch-pack: parse and
> advertise the object-format capability", 2020-05-27), perhaps as an
> oversight (the surrounding code at the point of this commit has already
> been using a request buffer.)

Good find.  Did this actually resulted in a data corruption and that
was how you discovered it?



>
> Signed-off-by: Jonathan Tan <jonathantanmy@google.com>
> ---
>  fetch-pack.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/fetch-pack.c b/fetch-pack.c
> index 6e68276aa3..2318ebe680 100644
> --- a/fetch-pack.c
> +++ b/fetch-pack.c
> @@ -1251,7 +1251,7 @@ static int send_fetch_request(struct fetch_negotiator *negotiator, int fd_out,
>  		if (hash_algo_by_ptr(the_hash_algo) != hash_algo)
>  			die(_("mismatched algorithms: client %s; server %s"),
>  			    the_hash_algo->name, hash_name);
> -		packet_write_fmt(fd_out, "object-format=%s", the_hash_algo->name);
> +		packet_buf_write(&req_buf, "object-format=%s", the_hash_algo->name);
>  	} else if (hash_algo_by_ptr(the_hash_algo) != GIT_HASH_SHA1) {
>  		die(_("the server does not support algorithm '%s'"),
>  		    the_hash_algo->name);

^ permalink raw reply	[flat|nested] 33+ messages in thread

* Re: [PATCH 2/6] fetch-pack: refactor process_acks()
  2021-04-09  1:09 ` [PATCH 2/6] fetch-pack: refactor process_acks() Jonathan Tan
@ 2021-04-09  5:08   ` Junio C Hamano
  2021-05-03 16:30   ` Derrick Stolee
  1 sibling, 0 replies; 33+ messages in thread
From: Junio C Hamano @ 2021-04-09  5:08 UTC (permalink / raw)
  To: Jonathan Tan; +Cc: git

Jonathan Tan <jonathantanmy@google.com> writes:

> A subsequent commit will need part, but not all, of the functionality in
> process_acks(), so move some of its functionality to its sole caller
> do_fetch_pack_v2(). As a side effect, the resulting code is also
> shorter.
>
> Signed-off-by: Jonathan Tan <jonathantanmy@google.com>
> ---
>  fetch-pack.c | 70 +++++++++++++++++-----------------------------------
>  1 file changed, 22 insertions(+), 48 deletions(-)

Nicely done.

I first found the patch hard to follow, but that wasn't due to this
patch, but because I wasn't all that familiar with the original
anymore (even though I do recall futzing with the codepath that
involves the in_vain stuff myself at some point in the past).

And indeed the resulting code is easy to see what is going on (I'd
need a lot more concentration than I can muster this late in the
night to be able to tell if the behaviour does not change with the
patch, though).

> diff --git a/fetch-pack.c b/fetch-pack.c
> index 2318ebe680..9f3901cdba 100644
> --- a/fetch-pack.c
> +++ b/fetch-pack.c
> @@ -1351,35 +1351,11 @@ static int process_section_header(struct packet_reader *reader,
>  	return ret;
>  }
>  
> -enum common_found {
> -	/*
> -	 * No commit was found to be possessed by both the client and the
> -	 * server, and "ready" was not received.
> -	 */
> -	NO_COMMON_FOUND,
> -
> -	/*
> -	 * At least one commit was found to be possessed by both the client and
> -	 * the server, and "ready" was not received.
> -	 */
> -	COMMON_FOUND,
> -
> -	/*
> -	 * "ready" was received, indicating that the server is ready to send
> -	 * the packfile without any further negotiation.
> -	 */
> -	READY
> -};
> -
> -static enum common_found process_acks(struct fetch_negotiator *negotiator,
> -				      struct packet_reader *reader,
> -				      struct oidset *common)
> +static int process_ack(struct fetch_negotiator *negotiator,
> +		       struct packet_reader *reader,
> +		       struct object_id *common_oid,
> +		       int *received_ready)
>  {
> -	/* received */
> -	int received_ready = 0;
> -	int received_ack = 0;
> -
> -	process_section_header(reader, "acknowledgments", 0);
>  	while (packet_reader_read(reader) == PACKET_READ_NORMAL) {
>  		const char *arg;
>  
> @@ -1387,20 +1363,17 @@ static enum common_found process_acks(struct fetch_negotiator *negotiator,
>  			continue;
>  
>  		if (skip_prefix(reader->line, "ACK ", &arg)) {
> -			struct object_id oid;
> -			received_ack = 1;
> -			if (!get_oid_hex(arg, &oid)) {
> +			if (!get_oid_hex(arg, common_oid)) {
>  				struct commit *commit;
> -				oidset_insert(common, &oid);
> -				commit = lookup_commit(the_repository, &oid);
> +				commit = lookup_commit(the_repository, common_oid);
>  				if (negotiator)
>  					negotiator->ack(negotiator, commit);
>  			}
> -			continue;
> +			return 1;
>  		}
>  
>  		if (!strcmp(reader->line, "ready")) {
> -			received_ready = 1;
> +			*received_ready = 1;
>  			continue;
>  		}
>  
> @@ -1418,13 +1391,12 @@ static enum common_found process_acks(struct fetch_negotiator *negotiator,
>  	 * sent. Therefore, a DELIM is expected if "ready" is sent, and a FLUSH
>  	 * otherwise.
>  	 */
> -	if (received_ready && reader->status != PACKET_READ_DELIM)
> +	if (*received_ready && reader->status != PACKET_READ_DELIM)
>  		die(_("expected packfile to be sent after 'ready'"));
> -	if (!received_ready && reader->status != PACKET_READ_FLUSH)
> +	if (!*received_ready && reader->status != PACKET_READ_FLUSH)
>  		die(_("expected no other sections to be sent after no 'ready'"));
>  
> -	return received_ready ? READY :
> -		(received_ack ? COMMON_FOUND : NO_COMMON_FOUND);
> +	return 0;
>  }
>  
>  static void receive_shallow_info(struct fetch_pack_args *args,
> @@ -1573,6 +1545,8 @@ static struct ref *do_fetch_pack_v2(struct fetch_pack_args *args,
>  	struct fetch_negotiator negotiator_alloc;
>  	struct fetch_negotiator *negotiator;
>  	int seen_ack = 0;
> +	struct object_id common_oid;
> +	int received_ready = 0;
>  	struct string_list packfile_uris = STRING_LIST_INIT_DUP;
>  	int i;
>  	struct strvec index_pack_args = STRVEC_INIT;
> @@ -1631,22 +1605,22 @@ static struct ref *do_fetch_pack_v2(struct fetch_pack_args *args,
>  			break;
>  		case FETCH_PROCESS_ACKS:
>  			/* Process ACKs/NAKs */
> -			switch (process_acks(negotiator, &reader, &common)) {
> -			case READY:
> +			process_section_header(&reader, "acknowledgments", 0);
> +			while (process_ack(negotiator, &reader, &common_oid,
> +					   &received_ready)) {
> +				in_vain = 0;
> +				seen_ack = 1;
> +				oidset_insert(&common, &common_oid);
> +			}
> +			if (received_ready) {
>  				/*
>  				 * Don't check for response delimiter; get_pack() will
>  				 * read the rest of this response.
>  				 */
>  				state = FETCH_GET_PACK;
> -				break;
> -			case COMMON_FOUND:
> -				in_vain = 0;
> -				seen_ack = 1;
> -				/* fallthrough */
> -			case NO_COMMON_FOUND:
> +			} else {
>  				do_check_stateless_delimiter(args, &reader);
>  				state = FETCH_SEND_REQUEST;
> -				break;
>  			}
>  			break;
>  		case FETCH_GET_PACK:

^ permalink raw reply	[flat|nested] 33+ messages in thread

* Re: [PATCH 3/6] fetch-pack: refactor add_haves()
  2021-04-09  1:10 ` [PATCH 3/6] fetch-pack: refactor add_haves() Jonathan Tan
@ 2021-04-09  5:20   ` Junio C Hamano
  0 siblings, 0 replies; 33+ messages in thread
From: Junio C Hamano @ 2021-04-09  5:20 UTC (permalink / raw)
  To: Jonathan Tan; +Cc: git

Jonathan Tan <jonathantanmy@google.com> writes:

> A subsequent commit will need part, but not all, of the functionality in
> add_haves(), so move some of its functionality to its sole caller
> send_fetch_request().
>
> Signed-off-by: Jonathan Tan <jonathantanmy@google.com>
> ---
>  fetch-pack.c | 28 ++++++++++++----------------
>  1 file changed, 12 insertions(+), 16 deletions(-)
>
> diff --git a/fetch-pack.c b/fetch-pack.c
> index 9f3901cdba..128ad47d2a 100644
> --- a/fetch-pack.c
> +++ b/fetch-pack.c
> @@ -1195,11 +1195,9 @@ static void add_common(struct strbuf *req_buf, struct oidset *common)
>  }
>  
>  static int add_haves(struct fetch_negotiator *negotiator,
> -		     int seen_ack,
>  		     struct strbuf *req_buf,
> -		     int *haves_to_send, int *in_vain)
> +		     int *haves_to_send)
>  {
> -	int ret = 0;
>  	int haves_added = 0;
>  	const struct object_id *oid;
>  
> @@ -1209,17 +1207,10 @@ static int add_haves(struct fetch_negotiator *negotiator,
>  			break;
>  	}
>  
> -	*in_vain += haves_added;
> -	if (!haves_added || (seen_ack && *in_vain >= MAX_IN_VAIN)) {
> -		/* Send Done */
> -		packet_buf_write(req_buf, "done\n");
> -		ret = 1;
> -	}
> -
>  	/* Increase haves to send on next round */
>  	*haves_to_send = next_flush(1, *haves_to_send);
>  
> -	return ret;
> +	return haves_added;
>  }

OK, so the helper used to

 - send out have's
 - increment *in_vain with the number of have's sent out
 - decide when to send done and send it
 - increase haves-to-send for the next round.

But the new version skips the second and third step, and let the
caller be responsible for in_vain management.  The only piece of
information the caller needs to do so from this function is the
number of have's we send out, so that is what we return from the
function.

> -	/* Add initial haves */
> -	ret = add_haves(negotiator, seen_ack, &req_buf,
> -			haves_to_send, in_vain);
> +	haves_added = add_haves(negotiator, &req_buf, haves_to_send);
> +	*in_vain += haves_added;
> +	if (!haves_added || (seen_ack && *in_vain >= MAX_IN_VAIN)) {
> +		/* Send Done */
> +		packet_buf_write(&req_buf, "done\n");
> +		done_sent = 1;
> +	}

And indeed, this caller does the *in_vain management add_haves()
used to do and give "done" as needed.

> @@ -1322,7 +1318,7 @@ static int send_fetch_request(struct fetch_negotiator *negotiator, int fd_out,
>  		die_errno(_("unable to write request to remote"));
>  
>  	strbuf_release(&req_buf);
> -	return ret;
> +	return done_sent;

And of course, the value returned by this function is if we sent
"done", which is far easier to see with the new variable name.

Again, very nicely done.


^ permalink raw reply	[flat|nested] 33+ messages in thread

* Re: [PATCH 4/6] fetch-pack: refactor command and capability write
  2021-04-09  1:10 ` [PATCH 4/6] fetch-pack: refactor command and capability write Jonathan Tan
@ 2021-04-09  5:27   ` Junio C Hamano
  0 siblings, 0 replies; 33+ messages in thread
From: Junio C Hamano @ 2021-04-09  5:27 UTC (permalink / raw)
  To: Jonathan Tan; +Cc: git

Jonathan Tan <jonathantanmy@google.com> writes:

> A subsequent commit will need this functionality independent of the rest
> of send_fetch_request(), so put this into its own function.

OK.  send_fetch_request() used to do the "command=fetch", capability
response, and concluded them with a delim packet, which is now done
with the new helper write_fetch_command_and_capabilities().

Mostly code movement, without any behaviour change.

Makes sense.

^ permalink raw reply	[flat|nested] 33+ messages in thread

* Re: [PATCH 5/6] fetch: teach independent negotiation (no packfile)
  2021-04-09  1:10 ` [PATCH 5/6] fetch: teach independent negotiation (no packfile) Jonathan Tan
@ 2021-04-09  5:41   ` Junio C Hamano
  2021-04-09 16:38     ` Jonathan Tan
  2021-05-03 15:25   ` Derrick Stolee
  1 sibling, 1 reply; 33+ messages in thread
From: Junio C Hamano @ 2021-04-09  5:41 UTC (permalink / raw)
  To: Jonathan Tan; +Cc: git

Jonathan Tan <jonathantanmy@google.com> writes:

> There are 2 code paths that do not go through fetch_refs_via_pack() that
> needed to be individually excluded: the bundle transport (excluded
> through requiring smart_options, which the bundle transport doesn't
> support) and transport helpers that do not support takeover.
> Fortunately, none of these support protocol v2.

I am a bit puzzled by this mention of "Fortunately".  If one says
"this shiny new feature only works with protocol v2" and "transport
X does not support protocol v2", doesn't it imply that the shiny new
feature cannot be used with the transport X, which is unfortunate?

I can understand "while interacting with the bundle transport, you
cannot do independent negotiation, but there is nothing to negotiate
with a static file that is a bundle anyway, so nothing is lost" as
an explanation, though.

>  Documentation/technical/protocol-v2.txt |  8 +++
>  builtin/fetch.c                         | 27 +++++++-
>  fetch-pack.c                            | 89 +++++++++++++++++++++++--
>  fetch-pack.h                            | 11 +++
>  object.h                                |  2 +-
>  t/t5701-git-serve.sh                    |  2 +-
>  t/t5702-protocol-v2.sh                  | 89 +++++++++++++++++++++++++
>  transport-helper.c                      | 10 +++
>  transport.c                             | 30 +++++++--
>  transport.h                             |  6 ++
>  upload-pack.c                           | 18 +++--
>  11 files changed, 275 insertions(+), 17 deletions(-)

It is a bit surprising that there isn't much code removed, as I
expected that we'd be factoring out and reusing existing code used
in negotiation for fetching into a new helper function (hence the
existing codepath would lose a lot of code to be replaced by a call
to a new helper function), but that is apparently not what is going
on.

I'll have to revisit this step and the next step tomorrow.

Thanks.

^ permalink raw reply	[flat|nested] 33+ messages in thread

* Re: [PATCH 1/6] fetch-pack: buffer object-format with other args
  2021-04-09  4:49   ` Junio C Hamano
@ 2021-04-09 16:24     ` Jonathan Tan
  0 siblings, 0 replies; 33+ messages in thread
From: Jonathan Tan @ 2021-04-09 16:24 UTC (permalink / raw)
  To: gitster; +Cc: jonathantanmy, git

> Jonathan Tan <jonathantanmy@google.com> writes:
> 
> > In send_fetch_request(), "object-format" is written directly to the file
> > descriptor, as opposed to the other arguments, which are buffered.
> > Buffer "object-format" as well. "object-format" must be buffered; in
> > particular, it must appear after "command=fetch" in the request.
> >
> > This divergence was introduced in 4b831208bb ("fetch-pack: parse and
> > advertise the object-format capability", 2020-05-27), perhaps as an
> > oversight (the surrounding code at the point of this commit has already
> > been using a request buffer.)
> 
> Good find.  Did this actually resulted in a data corruption and that
> was how you discovered it?

No, I did not see any data corruption. I discovered it because I was
looking at this function, thinking that I needed to refactor it.

^ permalink raw reply	[flat|nested] 33+ messages in thread

* Re: [PATCH 5/6] fetch: teach independent negotiation (no packfile)
  2021-04-09  5:41   ` Junio C Hamano
@ 2021-04-09 16:38     ` Jonathan Tan
  0 siblings, 0 replies; 33+ messages in thread
From: Jonathan Tan @ 2021-04-09 16:38 UTC (permalink / raw)
  To: gitster; +Cc: jonathantanmy, git

> Jonathan Tan <jonathantanmy@google.com> writes:
> 
> > There are 2 code paths that do not go through fetch_refs_via_pack() that
> > needed to be individually excluded: the bundle transport (excluded
> > through requiring smart_options, which the bundle transport doesn't
> > support) and transport helpers that do not support takeover.
> > Fortunately, none of these support protocol v2.
> 
> I am a bit puzzled by this mention of "Fortunately".  If one says
> "this shiny new feature only works with protocol v2" and "transport
> X does not support protocol v2", doesn't it imply that the shiny new
> feature cannot be used with the transport X, which is unfortunate?

I meant to say that we don't have to do much about these cases because
they are out of scope for the support that we planned (protocol v2), but
perhaps "fortunately" is the wrong way to say it. Perhaps a better way
of explaining it is that most code paths go through
fetch_refs_via_pack(), and for the ones that don't (bundle transport and
non-takeover transport helpers), we need to address them separately. But
in this case, we are not planning to support either, so we just check if
we have requested independent negotiation and if yes, report failure.

> I can understand "while interacting with the bundle transport, you
> cannot do independent negotiation, but there is nothing to negotiate
> with a static file that is a bundle anyway, so nothing is lost" as
> an explanation, though.
> 
> >  Documentation/technical/protocol-v2.txt |  8 +++
> >  builtin/fetch.c                         | 27 +++++++-
> >  fetch-pack.c                            | 89 +++++++++++++++++++++++--
> >  fetch-pack.h                            | 11 +++
> >  object.h                                |  2 +-
> >  t/t5701-git-serve.sh                    |  2 +-
> >  t/t5702-protocol-v2.sh                  | 89 +++++++++++++++++++++++++
> >  transport-helper.c                      | 10 +++
> >  transport.c                             | 30 +++++++--
> >  transport.h                             |  6 ++
> >  upload-pack.c                           | 18 +++--
> >  11 files changed, 275 insertions(+), 17 deletions(-)
> 
> It is a bit surprising that there isn't much code removed, as I
> expected that we'd be factoring out and reusing existing code used
> in negotiation for fetching into a new helper function (hence the
> existing codepath would lose a lot of code to be replaced by a call
> to a new helper function), but that is apparently not what is going
> on.

That's what I was trying to do (hence the earlier patches), but the main
thing I ran into is that a lot of the fetch code assumes that you're
fetching at least one ref, so I couldn't use a lot of it without more
code updating. Having said that, I may have missed more opportunities
for reuse.

> I'll have to revisit this step and the next step tomorrow.
> 
> Thanks.

Thanks for taking a look.

^ permalink raw reply	[flat|nested] 33+ messages in thread

* Re: [PATCH 0/6] Push negotiation
  2021-04-09  1:09 [PATCH 0/6] Push negotiation Jonathan Tan
                   ` (5 preceding siblings ...)
  2021-04-09  1:10 ` [PATCH 6/6] send-pack: support push negotiation Jonathan Tan
@ 2021-04-30  5:42 ` Junio C Hamano
  2021-04-30 17:33   ` Derrick Stolee
  2021-05-04 21:15 ` [PATCH v2 0/5] " Jonathan Tan
  7 siblings, 1 reply; 33+ messages in thread
From: Junio C Hamano @ 2021-04-30  5:42 UTC (permalink / raw)
  To: git; +Cc: Jonathan Tan

Jonathan Tan <jonathantanmy@google.com> writes:

> Here are patches for push negotiation. The basic idea is that we can
> reuse part of the fetch protocol (and code) to find out what is in
> common between the client and server, and then use that information to
> further narrow the objects sent in the packfile during a push.
>
> Patch 1 is a bug fix that probably should be merged even if the rest
> aren't. Patches 2-4 are refactorings in preparation for the future
> patches. Patches 5-6 contain the actual logic and documentation.
>
> I have written more about it in my prior work [1], although the commit
> messages and documentation in patches 5-6 should be enough to explain
> what's going on. (If they're not, feel free to make review comments.)
>
> The main change from [1] is that the client-side code that used to be in
> builtin/fetch-pack.c is now in builtin/fetch.c, because I realized that
> builtin/fetch-pack.c does not support HTTP. Other than that, all the
> "what hasn't been done yet" items have been done except for statistics
> in the commit message.
>
> [1] https://lore.kernel.org/git/20210218012100.928957-1-jonathantanmy@google.com/

So... anybody else wants to review this and give it a-OK?

> Jonathan Tan (6):
>   fetch-pack: buffer object-format with other args
>   fetch-pack: refactor process_acks()
>   fetch-pack: refactor add_haves()
>   fetch-pack: refactor command and capability write
>   fetch: teach independent negotiation (no packfile)
>   send-pack: support push negotiation
>
>  Documentation/config/push.txt           |   7 +
>  Documentation/technical/protocol-v2.txt |   8 +
>  builtin/fetch.c                         |  27 ++-
>  fetch-pack.c                            | 224 +++++++++++++++---------
>  fetch-pack.h                            |  11 ++
>  object.h                                |   2 +-
>  send-pack.c                             |  61 ++++++-
>  t/t5516-fetch-push.sh                   |  35 ++++
>  t/t5701-git-serve.sh                    |   2 +-
>  t/t5702-protocol-v2.sh                  |  89 ++++++++++
>  transport-helper.c                      |  10 ++
>  transport.c                             |  30 +++-
>  transport.h                             |   6 +
>  upload-pack.c                           |  18 +-
>  14 files changed, 430 insertions(+), 100 deletions(-)

^ permalink raw reply	[flat|nested] 33+ messages in thread

* Re: [PATCH 0/6] Push negotiation
  2021-04-30  5:42 ` [PATCH 0/6] Push negotiation Junio C Hamano
@ 2021-04-30 17:33   ` Derrick Stolee
  0 siblings, 0 replies; 33+ messages in thread
From: Derrick Stolee @ 2021-04-30 17:33 UTC (permalink / raw)
  To: Junio C Hamano, git; +Cc: Jonathan Tan

On 4/30/2021 1:42 AM, Junio C Hamano wrote:
> Jonathan Tan <jonathantanmy@google.com> writes:
> 
>> Here are patches for push negotiation. The basic idea is that we can
>> reuse part of the fetch protocol (and code) to find out what is in
>> common between the client and server, and then use that information to
>> further narrow the objects sent in the packfile during a push.
>>
>> Patch 1 is a bug fix that probably should be merged even if the rest
>> aren't. Patches 2-4 are refactorings in preparation for the future
>> patches. Patches 5-6 contain the actual logic and documentation.
>>
>> I have written more about it in my prior work [1], although the commit
>> messages and documentation in patches 5-6 should be enough to explain
>> what's going on. (If they're not, feel free to make review comments.)
>>
>> The main change from [1] is that the client-side code that used to be in
>> builtin/fetch-pack.c is now in builtin/fetch.c, because I realized that
>> builtin/fetch-pack.c does not support HTTP. Other than that, all the
>> "what hasn't been done yet" items have been done except for statistics
>> in the commit message.
>>
>> [1] https://lore.kernel.org/git/20210218012100.928957-1-jonathantanmy@google.com/
> 
> So... anybody else wants to review this and give it a-OK?

I put this on my calendar for Monday morning. I hope that's not too
long to wait.

Thanks,
-Stolee

^ permalink raw reply	[flat|nested] 33+ messages in thread

* Re: [PATCH 5/6] fetch: teach independent negotiation (no packfile)
  2021-04-09  1:10 ` [PATCH 5/6] fetch: teach independent negotiation (no packfile) Jonathan Tan
  2021-04-09  5:41   ` Junio C Hamano
@ 2021-05-03 15:25   ` Derrick Stolee
  2021-05-03 15:40     ` Derrick Stolee
  2021-05-03 21:52     ` Jonathan Tan
  1 sibling, 2 replies; 33+ messages in thread
From: Derrick Stolee @ 2021-05-03 15:25 UTC (permalink / raw)
  To: Jonathan Tan, git

On 4/8/21 9:10 PM, Jonathan Tan wrote:
> Currently, the packfile negotiation step within a Git fetch cannot be
> done independent of sending the packfile, even though there is at least
> one application wherein this is useful. Therefore, make it possible for
> this negotiation step to be done independently. A subsequent commit will
> use this for one such application - push negotiation.
...
> --- a/Documentation/technical/protocol-v2.txt
> +++ b/Documentation/technical/protocol-v2.txt
> @@ -346,6 +346,14 @@ explained below.
>  	client should download from all given URIs. Currently, the
>  	protocols supported are "http" and "https".
>  
> +If the 'wait-for-done' feature is advertised, the following argument
> +can be included in the client's request.
> +
> +    wait-for-done
> +	Indicates to the server that it should never send "ready", but
> +	should wait for the client to say "done" before sending the
> +	packfile.
> +

Ok, this is a good way to handle the compatibility case. I'll check
in the next patch how this feature is checked before sending a pack-file
in 'git push'.

> @@ -202,6 +203,8 @@ static struct option builtin_fetch_options[] = {
>  			TRANSPORT_FAMILY_IPV6),
>  	OPT_STRING_LIST(0, "negotiation-tip", &negotiation_tip, N_("revision"),
>  			N_("report that we have only objects reachable from this object")),
> +	OPT_BOOL(0, "negotiate-only", &negotiate_only,
> +		 N_("do not fetch a packfile; instead, print ancestors of negotiation tips")),

It seems a little strange for this step, which is mostly used for tests,
to be so visible. I think it would be too much work to create a test
helper with an equivalent implementation, so maybe describe this option
as only for tests in Documentation/git-fetch.txt.
  
> -	if (remote) {
> +	if (negotiate_only) {
> +		struct oidset acked_commits = OIDSET_INIT;
> +		struct oidset_iter iter;
> +		const struct object_id *oid;
> +
> +		if (!remote)
> +			die(_("Must supply remote when using --negotiate-only"));

Please use lowercase letters to start your error messages.

> +		gtransport = prepare_transport(remote, 1);
> +		if (gtransport->smart_options) {
> +			gtransport->smart_options->acked_commits = &acked_commits;
> +		} else {
> +			warning(_("Protocol does not support --negotiate-only, exiting."));
> +			return 1;
> +		}
> +		if (server_options.nr)
> +			gtransport->server_options = &server_options;
> +		result = transport_fetch_refs(gtransport, NULL);
> +
> +		oidset_iter_init(&acked_commits, &iter);
> +		while ((oid = oidset_iter_next(&iter)))
> +			printf("%s\n", oid_to_hex(oid));
> +		oidset_clear(&acked_commits);
> +	} else if (remote) {

...

> +static int add_to_object_array(const struct object_id *oid, void *data)
> +{
> +	struct object_array *a = data;
> +
> +	add_object_array(parse_object(the_repository, oid), "", a);
> +	return 0;
> +}

Why parse_object() over lookup_object()?

> +void negotiate_using_fetch(const struct oid_array *negotiation_tips,
> +			   const struct string_list *server_options,
> +			   int stateless_rpc,
> +			   int fd[],
> +			   struct oidset *acked_commits)

It might be worth a careful doc comment to say that we _must_
have already verified the wait-for-done capability.

> +{
> +	struct fetch_negotiator negotiator;
> +	struct packet_reader reader;
> +	struct object_array nt_object_array = OBJECT_ARRAY_INIT;
> +	struct strbuf req_buf = STRBUF_INIT;
> +	int haves_to_send = INITIAL_FLUSH;
> +	int in_vain = 0;
> +	int seen_ack = 0;
> +	int last_iteration = 0;

As will become clear later, create:

	timestamp_t min_generation = GENERATION_NUMBER_INFINITY;

> +
> +	fetch_negotiator_init(the_repository, &negotiator);
> +	mark_tips(&negotiator, negotiation_tips);
> +
> +	packet_reader_init(&reader, fd[0], NULL, 0,
> +			   PACKET_READ_CHOMP_NEWLINE |
> +			   PACKET_READ_DIE_ON_ERR_PACKET);
> +
> +	oid_array_for_each((struct oid_array *) negotiation_tips,
> +			   add_to_object_array,
> +			   &nt_object_array);
> +
> +	while (!last_iteration) {
> +		int haves_added;
> +		struct object_id common_oid;
> +		int received_ready = 0;
> +
> +		strbuf_reset(&req_buf);
> +		write_fetch_command_and_capabilities(&req_buf, server_options);
> +
> +		packet_buf_write(&req_buf, "wait-for-done");
> +
> +		haves_added = add_haves(&negotiator, &req_buf, &haves_to_send);
> +		in_vain += haves_added;
> +		if (!haves_added || (seen_ack && in_vain >= MAX_IN_VAIN))
> +			last_iteration = 1;
> +
> +		/* Send request */
> +		packet_buf_flush(&req_buf);
> +		if (write_in_full(fd[1], req_buf.buf, req_buf.len) < 0)
> +			die_errno(_("unable to write request to remote"));
> +
> +		/* Process ACKs/NAKs */
> +		process_section_header(&reader, "acknowledgments", 0);
> +		while (process_ack(&negotiator, &reader, &common_oid,
> +				   &received_ready)) {
> +			struct commit *commit = lookup_commit(the_repository,
> +							      &common_oid);
> +			if (commit)
> +				commit->object.flags |= COMMON;

Making note of this portion of the code: you can update a min_generation
value here, decreasing it if we see a smaller generation.

> +			in_vain = 0;
> +			seen_ack = 1;
> +			oidset_insert(acked_commits, &common_oid);
> +		}
> +		if (received_ready)
> +			die(_("unexpected 'ready' from remote"));
> +		else
> +			do_check_stateless_delimiter(stateless_rpc, &reader);
> +		if (can_all_from_reach_with_flag(&nt_object_array, COMMON,
> +						 REACH_SCRATCH, 0,
> +						 GENERATION_NUMBER_ZERO))

And finally here you can use min_generation. Otherwise, you will suffer
performance problems when there is a deep history but this returns false.

As long as min_generation is the minimum generation of a commit with the
COMMON flag, you will be correct to use that limit.

> +			last_iteration = 1;
> +	}
> +	strbuf_release(&req_buf);

Don't forget to clear the COMMON flag before returning.

> +}
> +

> +/*
> + * Execute the --negotiate-only mode of "git fetch", adding all known common
> + * commits to acked_commits.
> + */> +void negotiate_using_fetch(const struct oid_array *negotiation_tips,
> +			   const struct string_list *server_options,
> +			   int stateless_rpc,
> +			   int fd[],
> +			   struct oidset *acked_commits);

Here is a good place to specifically mention the wait-for-done capability,
or else this method will die() when seeing the "ready" from the server.

> +setup_negotiate_only () {
> +	SERVER="$1"
> +	URI="$2"
> +
> +	rm -rf "$SERVER" client
> +
> +	git init "$SERVER"
> +	test_commit -C "$SERVER" one
> +	test_commit -C "$SERVER" two
> +
> +	git clone "$URI" client
> +	test_commit -C client three
> +}
> +
> +test_expect_success 'file:// --negotiate-only' '
> +	SERVER="server" &&
> +	URI="file://$(pwd)/server" &&
> +
> +	setup_negotiate_only "$SERVER" "$URI" &&
> +
> +	git -C client fetch \
> +		--no-tags \
> +		--negotiate-only \
> +		--negotiation-tip=$(git -C client rev-parse HEAD) \
> +		origin >out &&
> +	COMMON=$(git -C "$SERVER" rev-parse two) &&
> +	grep "$COMMON" out
> +'
> +
> +test_expect_success 'file:// --negotiate-only with protocol v0' '
> +	SERVER="server" &&
> +	URI="file://$(pwd)/server" &&
> +
> +	setup_negotiate_only "$SERVER" "$URI" &&
> +
> +	test_must_fail git -c protocol.version=0 -C client fetch \
> +		--no-tags \
> +		--negotiate-only \
> +		--negotiation-tip=$(git -C client rev-parse HEAD) \
> +		origin 2>err &&
> +	test_i18ngrep "negotiate-only requires protocol v2" err
> +'
> +
>  # Test protocol v2 with 'http://' transport
>  #
>  . "$TEST_DIRECTORY"/lib-httpd.sh
> @@ -1035,6 +1078,52 @@ test_expect_success 'packfile-uri with transfer.fsckobjects fails when .gitmodul
>  	test_i18ngrep "disallowed submodule name" err
>  '
>  
> +test_expect_success 'http:// --negotiate-only' '
> +	SERVER="$HTTPD_DOCUMENT_ROOT_PATH/server" &&
> +	URI="$HTTPD_URL/smart/server" &&
> +
> +	setup_negotiate_only "$SERVER" "$URI" &&
> +
> +	git -C client fetch \
> +		--no-tags \
> +		--negotiate-only \
> +		--negotiation-tip=$(git -C client rev-parse HEAD) \
> +		origin >out &&
> +	COMMON=$(git -C "$SERVER" rev-parse two) &&
> +	grep "$COMMON" out
> +'
> +
> +test_expect_success 'http:// --negotiate-only without wait-for-done support' '
> +	SERVER="server" &&
> +	URI="$HTTPD_URL/one_time_perl/server" &&
> +
> +	setup_negotiate_only "$SERVER" "$URI" &&
> +
> +	echo "s/ wait-for-done/ xxxx-xxx-xxxx/" \
> +		>"$HTTPD_ROOT_PATH/one-time-perl" &&
> +
> +	test_must_fail git -C client fetch \
> +		--no-tags \
> +		--negotiate-only \
> +		--negotiation-tip=$(git -C client rev-parse HEAD) \
> +		origin 2>err &&
> +	test_i18ngrep "server does not support wait-for-done" err
> +'
> +
> +test_expect_success 'http:// --negotiate-only with protocol v0' '
> +	SERVER="$HTTPD_DOCUMENT_ROOT_PATH/server" &&
> +	URI="$HTTPD_URL/smart/server" &&
> +
> +	setup_negotiate_only "$SERVER" "$URI" &&
> +
> +	test_must_fail git -c protocol.version=0 -C client fetch \
> +		--no-tags \
> +		--negotiate-only \
> +		--negotiation-tip=$(git -C client rev-parse HEAD) \
> +		origin 2>err &&
> +	test_i18ngrep "negotiate-only requires protocol v2" err
> +'
> +
>  # DO NOT add non-httpd-specific tests here, because the last part of this
>  # test script is only executed when httpd is available and enabled.
>  
> diff --git a/transport-helper.c b/transport-helper.c
> index 4cd76366fa..4be035edb8 100644
> --- a/transport-helper.c
> +++ b/transport-helper.c
> @@ -684,6 +684,16 @@ static int fetch(struct transport *transport,
>  		return transport->vtable->fetch(transport, nr_heads, to_fetch);
>  	}
>  
> +	/*
> +	 * If we reach here, then the server, the client, and/or the transport
> +	 * helper does not support protocol v2. --negotiate-only requires
> +	 * protocol v2.
> +	 */
> +	if (data->transport_options.acked_commits) {
> +		warning(_("--negotiate-only requires protocol v2"));
> +		return -1;
> +	}
> +

This method continues to do a lot that doesn't seem specific to
--negotiate-only. The warning message seems incorrect to me, but
is also seems like this would break several cases when using
protocol v0. It is equally possible that I'm misunderstanding
what is going on here.

> +	if (data->options.acked_commits) {
> +		if (data->version < protocol_v2) {
> +			warning(_("--negotiate-only requires protocol v2"));
> +			ret = -1;
> +		} else if (!server_supports_feature("fetch", "wait-for-done", 0)) {
> +			warning(_("server does not support wait-for-done"));
> +			ret = -1;
> +		} else {
> +			negotiate_using_fetch(data->options.negotiation_tips,
> +					      transport->server_options,
> +					      transport->stateless_rpc,
> +					      data->fd,
> +					      data->options.acked_commits);
> +			ret = 0;
> +		}
> +		goto cleanup;
> +	}

These prereqs look right. This makes it look rather strange that
negotiate_using_fetch() returns void (and has several die() calls inside)
and could instead return an 'int' that is consumed here (and use
error() calls instead of die()).

>  	refs = fetch_pack(&args, data->fd,
>  			  refs_tmp ? refs_tmp : transport->remote_refs,
>  			  to_fetch, nr_heads, &data->shallow,
>  			  &transport->pack_lockfiles, data->version);
>  
> -	close(data->fd[0]);
> -	close(data->fd[1]);
> -	if (finish_connect(data->conn))
> -		ret = -1;
> -	data->conn = NULL;
...

> +cleanup:
> +	close(data->fd[0]);
> +	close(data->fd[1]);
> +	if (finish_connect(data->conn))
> +		ret = -1;
> +	data->conn = NULL;
> +

Good to keep these after skipping a big chunk of the fetch logic.

> +
> +	/*
> +	 * If set, whenever transport_fetch_refs() is called, add known common
> +	 * commits to this oidset instead of fetching any packfiles.
> +	 */
> +	struct oidset *acked_commits;

nit: s/If set/If allocated/

> @@ -1668,10 +1673,13 @@ int upload_pack_v2(struct repository *r, struct strvec *keys,
>  		case FETCH_PROCESS_ARGS:
>  			process_args(request, &data);
>  
> -			if (!data.want_obj.nr) {
> +			if (!data.want_obj.nr && !data.wait_for_done) {
>  				/*
> -				 * Request didn't contain any 'want' lines,
> -				 * guess they didn't want anything.
> +				 * Request didn't contain any 'want' lines (and
> +				 * the request does not contain
> +				 * "wait-for-done", in which it is reasonable
> +				 * to just send 'have's without 'want's); guess
> +				 * they didn't want anything.
>  				 */
>  				state = FETCH_DONE;
>  			} else if (data.haves.nr) {
> @@ -1723,7 +1731,7 @@ int upload_pack_advertise(struct repository *r,
>  		int allow_sideband_all_value;
>  		char *str = NULL;
>  
> -		strbuf_addstr(value, "shallow");
> +		strbuf_addstr(value, "shallow wait-for-done");

It might be nice to have this wait-for-done capability configurable.
I'd likely want this on by default, but in case there is an issue it
is easier to change config values than ship new binaries.

This is a pretty big patch. It might have been nice to split the
server-side stuff out as its own patch with a follow-up for the client
code and the tests.

Thanks,
-Stolee

^ permalink raw reply	[flat|nested] 33+ messages in thread

* Re: [PATCH 6/6] send-pack: support push negotiation
  2021-04-09  1:10 ` [PATCH 6/6] send-pack: support push negotiation Jonathan Tan
@ 2021-05-03 15:35   ` Derrick Stolee
  2021-05-03 22:02     ` Jonathan Tan
  0 siblings, 1 reply; 33+ messages in thread
From: Derrick Stolee @ 2021-05-03 15:35 UTC (permalink / raw)
  To: Jonathan Tan, git

On 4/8/21 9:10 PM, Jonathan Tan wrote:
> Teach Git the push.negotiate config variable.
...
> +push.negotiate::
> +	If set to "true", attempt to reduce the size of the packfile
> +	sent by rounds of negotiation in which the client and the
> +	server attempt to find commits in common. If "false", Git will
> +	rely solely on the server's ref advertisement to find commits
> +	in common.

Works for me.

> diff --git a/send-pack.c b/send-pack.c
> index 5f215b13c7..9cb9f71650 100644
> --- a/send-pack.c
> +++ b/send-pack.c
> @@ -56,7 +56,9 @@ static void feed_object(const struct object_id *oid, FILE *fh, int negative)
>  /*
>   * Make a pack stream and spit it out into file descriptor fd
>   */
> -static int pack_objects(int fd, struct ref *refs, struct oid_array *extra, struct send_pack_args *args)
> +static int pack_objects(int fd, struct ref *refs, struct oid_array *advertised,
> +			struct oid_array *negotiated,
> +			struct send_pack_args *args)

At the moment, I don't see why we need two oid_arrays here.
Instead, this 'extra' could instead be renamed to something
like 'server_objects' or 'base_objects' to make it clear
that we don't want those objects, and can even use them and
their reachable objects as delta bases, when appropriate.

Or, just don't touch it.

> +static void get_commons_through_negotiation(const char *url,
> +					    const struct ref *remote_refs,
> +					    struct oid_array *commons)
> +{
> +	struct child_process child = CHILD_PROCESS_INIT;
> +	const struct ref *ref;
> +	int len = the_hash_algo->hexsz + 1; /* hash + NL */
> +
> +	child.git_cmd = 1;
> +	child.no_stdin = 1;
> +	child.out = -1;
> +	strvec_pushl(&child.args, "fetch", "--negotiate-only", NULL);
> +	for (ref = remote_refs; ref; ref = ref->next)
> +		strvec_pushf(&child.args, "--negotiation-tip=%s", oid_to_hex(&ref->new_oid));
> +	strvec_push(&child.args, url);

Oh! We are using a 'git fetch --negotiate-only' subprocess here. You
can ignore my previous message about updating the docs for this to be
used only by tests.

> +
> +	if (start_command(&child))
> +		die(_("send-pack: unable to fork off fetch subprocess"));
> +
> +	do {
> +		char hex_hash[GIT_MAX_HEXSZ + 1];
> +		int read_len = read_in_full(child.out, hex_hash, len);
> +		struct object_id oid;
> +		const char *end;
> +
> +		if (!read_len)
> +			break;
> +		if (read_len != len)
> +			die("invalid length read %d", read_len);
> +		if (parse_oid_hex(hex_hash, &oid, &end) || *end != '\n')
> +			die("invalid hash");
> +		oid_array_append(commons, &oid);
This appends, so there is no reason why it needs to be empty before
the method. Is there a way we could feed the extra_have set when
calling this method? Or is it happening at a strange time?

> +	} while (1);
> +
> +	if (finish_command(&child)) {
> +		/*
> +		 * The information that push negotiation provides is useful but
> +		 * not mandatory.
> +		 */
> +		warning(_("push negotiation failed; proceeding anyway with push"));
> +	}
> +}
> +
>  int send_pack(struct send_pack_args *args,
>  	      int fd[], struct child_process *conn,
>  	      struct ref *remote_refs,
>  	      struct oid_array *extra_have)
>  {
> +	struct oid_array commons = OID_ARRAY_INIT;
>  	int in = fd[0];
>  	int out = fd[1];
>  	struct strbuf req_buf = STRBUF_INIT;
> @@ -426,6 +474,7 @@ int send_pack(struct send_pack_args *args,
>  	int quiet_supported = 0;
>  	int agent_supported = 0;
>  	int advertise_sid = 0;
> +	int push_negotiate = 0;
>  	int use_atomic = 0;
>  	int atomic_supported = 0;
>  	int use_push_options = 0;
> @@ -437,6 +486,10 @@ int send_pack(struct send_pack_args *args,
>  	const char *push_cert_nonce = NULL;
>  	struct packet_reader reader;
>  
> +	git_config_get_bool("push.negotiate", &push_negotiate);
> +	if (push_negotiate)
> +		get_commons_through_negotiation(args->url, remote_refs, &commons);
> +
>  	git_config_get_bool("transfer.advertisesid", &advertise_sid);
>  
>  	/* Does the other end support the reporting? */
> @@ -625,7 +678,7 @@ int send_pack(struct send_pack_args *args,
>  			   PACKET_READ_DIE_ON_ERR_PACKET);
>  
>  	if (need_pack_data && cmds_sent) {
> -		if (pack_objects(out, remote_refs, extra_have, args) < 0) {
> +		if (pack_objects(out, remote_refs, extra_have, &commons, args) < 0) {

Here, it would be nice if extra_have and commons were merged before calling
pack_objects(). I mentioned a way to perhaps make that easier above, but
the context might not make that be super-simple. Running a loop here to
scan 'commons' and append them to 'extra_have' might be a sufficient
approach.

Generally, this approach seems like it would work. I have not done any
local testing, yet.

Thanks,
-Stolee


^ permalink raw reply	[flat|nested] 33+ messages in thread

* Re: [PATCH 5/6] fetch: teach independent negotiation (no packfile)
  2021-05-03 15:25   ` Derrick Stolee
@ 2021-05-03 15:40     ` Derrick Stolee
  2021-05-03 21:52     ` Jonathan Tan
  1 sibling, 0 replies; 33+ messages in thread
From: Derrick Stolee @ 2021-05-03 15:40 UTC (permalink / raw)
  To: Jonathan Tan, git

On 5/3/21 11:25 AM, Derrick Stolee wrote:
> On 4/8/21 9:10 PM, Jonathan Tan wrote:
>> Currently, the packfile negotiation step within a Git fetch cannot be
>> done independent of sending the packfile, even though there is at least
>> one application wherein this is useful. Therefore, make it possible for
>> this negotiation step to be done independently. A subsequent commit will
>> use this for one such application - push negotiation.
> ...
>> diff --git a/transport-helper.c b/transport-helper.c
>> index 4cd76366fa..4be035edb8 100644
>> --- a/transport-helper.c
>> +++ b/transport-helper.c
>> @@ -684,6 +684,16 @@ static int fetch(struct transport *transport,
>>  		return transport->vtable->fetch(transport, nr_heads, to_fetch);
>>  	}
>>  
>> +	/*
>> +	 * If we reach here, then the server, the client, and/or the transport
>> +	 * helper does not support protocol v2. --negotiate-only requires
>> +	 * protocol v2.
>> +	 */
>> +	if (data->transport_options.acked_commits) {
>> +		warning(_("--negotiate-only requires protocol v2"));
>> +		return -1;
>> +	}
>> +
> 
> This method continues to do a lot that doesn't seem specific to
> --negotiate-only. The warning message seems incorrect to me, but
> is also seems like this would break several cases when using
> protocol v0. It is equally possible that I'm misunderstanding
> what is going on here.

I didn't see this cause any failures when running the test suite
with GIT_TEST_PROTOCOL_VERSION=0, but I _do_ see failures in your
tests added in PATCH 6 with that environment variable set. You
might want to set it manually in the important test cases.

Thanks,
-Stolee


^ permalink raw reply	[flat|nested] 33+ messages in thread

* Re: [PATCH 2/6] fetch-pack: refactor process_acks()
  2021-04-09  1:09 ` [PATCH 2/6] fetch-pack: refactor process_acks() Jonathan Tan
  2021-04-09  5:08   ` Junio C Hamano
@ 2021-05-03 16:30   ` Derrick Stolee
  1 sibling, 0 replies; 33+ messages in thread
From: Derrick Stolee @ 2021-05-03 16:30 UTC (permalink / raw)
  To: Jonathan Tan, git

On 4/8/21 9:09 PM, Jonathan Tan wrote:
> A subsequent commit will need part, but not all, of the functionality in
> process_acks(), so move some of its functionality to its sole caller
> do_fetch_pack_v2(). As a side effect, the resulting code is also
> shorter.
>  		case FETCH_PROCESS_ACKS:
>  			/* Process ACKs/NAKs */
> -			switch (process_acks(negotiator, &reader, &common)) {

Good riddance to this nested switch!

I am unfamiliar with this code, but I believe these changes to
be correct.

Thanks,
-Stolee

^ permalink raw reply	[flat|nested] 33+ messages in thread

* Re: [PATCH 5/6] fetch: teach independent negotiation (no packfile)
  2021-05-03 15:25   ` Derrick Stolee
  2021-05-03 15:40     ` Derrick Stolee
@ 2021-05-03 21:52     ` Jonathan Tan
  1 sibling, 0 replies; 33+ messages in thread
From: Jonathan Tan @ 2021-05-03 21:52 UTC (permalink / raw)
  To: stolee; +Cc: jonathantanmy, git

> On 4/8/21 9:10 PM, Jonathan Tan wrote:
> > Currently, the packfile negotiation step within a Git fetch cannot be
> > done independent of sending the packfile, even though there is at least
> > one application wherein this is useful. Therefore, make it possible for
> > this negotiation step to be done independently. A subsequent commit will
> > use this for one such application - push negotiation.
> ...
> > --- a/Documentation/technical/protocol-v2.txt
> > +++ b/Documentation/technical/protocol-v2.txt
> > @@ -346,6 +346,14 @@ explained below.
> >  	client should download from all given URIs. Currently, the
> >  	protocols supported are "http" and "https".
> >  
> > +If the 'wait-for-done' feature is advertised, the following argument
> > +can be included in the client's request.
> > +
> > +    wait-for-done
> > +	Indicates to the server that it should never send "ready", but
> > +	should wait for the client to say "done" before sending the
> > +	packfile.
> > +
> 
> Ok, this is a good way to handle the compatibility case. I'll check
> in the next patch how this feature is checked before sending a pack-file
> in 'git push'.

Thanks.

> > @@ -202,6 +203,8 @@ static struct option builtin_fetch_options[] = {
> >  			TRANSPORT_FAMILY_IPV6),
> >  	OPT_STRING_LIST(0, "negotiation-tip", &negotiation_tip, N_("revision"),
> >  			N_("report that we have only objects reachable from this object")),
> > +	OPT_BOOL(0, "negotiate-only", &negotiate_only,
> > +		 N_("do not fetch a packfile; instead, print ancestors of negotiation tips")),
> 
> It seems a little strange for this step, which is mostly used for tests,
> to be so visible. I think it would be too much work to create a test
> helper with an equivalent implementation, so maybe describe this option
> as only for tests in Documentation/git-fetch.txt.

As you mention in your review of the subsequent patch [1], this is
because we're calling "fetch" as a subprocess from "push", so it needs
to accept command-line arguments specifying that we're not interested in
the packfile.

[1] https://lore.kernel.org/git/c2780570-81ec-bede-2f4e-75748b788bbb@gmail.com/

> > -	if (remote) {
> > +	if (negotiate_only) {
> > +		struct oidset acked_commits = OIDSET_INIT;
> > +		struct oidset_iter iter;
> > +		const struct object_id *oid;
> > +
> > +		if (!remote)
> > +			die(_("Must supply remote when using --negotiate-only"));
> 
> Please use lowercase letters to start your error messages.

Thanks - done.

> > +static int add_to_object_array(const struct object_id *oid, void *data)
> > +{
> > +	struct object_array *a = data;
> > +
> > +	add_object_array(parse_object(the_repository, oid), "", a);
> > +	return 0;
> > +}
> 
> Why parse_object() over lookup_object()?

Switched to lookup_object(). I don't think it matters here because we'll
need to parse all commits when doing negotiation anyway (to find their
parents), but I changed it to avoid confusion.

> > +void negotiate_using_fetch(const struct oid_array *negotiation_tips,
> > +			   const struct string_list *server_options,
> > +			   int stateless_rpc,
> > +			   int fd[],
> > +			   struct oidset *acked_commits)
> 
> It might be worth a careful doc comment to say that we _must_
> have already verified the wait-for-done capability.

OK - written in the .h file.

[snip min_generation explanation]

> And finally here you can use min_generation. Otherwise, you will suffer
> performance problems when there is a deep history but this returns false.
> 
> As long as min_generation is the minimum generation of a commit with the
> COMMON flag, you will be correct to use that limit.

Thanks for the precise guidance of how to use generation numbers to
speed things up. I've implemented your suggestions.

> 
> > +			last_iteration = 1;
> > +	}
> > +	strbuf_release(&req_buf);
> 
> Don't forget to clear the COMMON flag before returning.

OK - done. (I don't think it matters here, but I guess it's clearer if
we do as you suggest. The loop will take some time to run, but it's
small compared to the network time needed anyway.)

> > +/*
> > + * Execute the --negotiate-only mode of "git fetch", adding all known common
> > + * commits to acked_commits.
> > + */> +void negotiate_using_fetch(const struct oid_array *negotiation_tips,
> > +			   const struct string_list *server_options,
> > +			   int stateless_rpc,
> > +			   int fd[],
> > +			   struct oidset *acked_commits);
> 
> Here is a good place to specifically mention the wait-for-done capability,
> or else this method will die() when seeing the "ready" from the server.

Acknowledged.

> > diff --git a/transport-helper.c b/transport-helper.c
> > index 4cd76366fa..4be035edb8 100644
> > --- a/transport-helper.c
> > +++ b/transport-helper.c
> > @@ -684,6 +684,16 @@ static int fetch(struct transport *transport,
> >  		return transport->vtable->fetch(transport, nr_heads, to_fetch);
> >  	}
> >  
> > +	/*
> > +	 * If we reach here, then the server, the client, and/or the transport
> > +	 * helper does not support protocol v2. --negotiate-only requires
> > +	 * protocol v2.
> > +	 */
> > +	if (data->transport_options.acked_commits) {
> > +		warning(_("--negotiate-only requires protocol v2"));
> > +		return -1;
> > +	}
> > +
> 
> This method continues to do a lot that doesn't seem specific to
> --negotiate-only. The warning message seems incorrect to me, but
> is also seems like this would break several cases when using
> protocol v0. It is equally possible that I'm misunderstanding
> what is going on here.

It's specific to --negotiate-only in that acked_commits is set if and
only if we use --negotiate-only. What cases are you think of that break
when using protocol v0?

> > +	if (data->options.acked_commits) {
> > +		if (data->version < protocol_v2) {
> > +			warning(_("--negotiate-only requires protocol v2"));
> > +			ret = -1;
> > +		} else if (!server_supports_feature("fetch", "wait-for-done", 0)) {
> > +			warning(_("server does not support wait-for-done"));
> > +			ret = -1;
> > +		} else {
> > +			negotiate_using_fetch(data->options.negotiation_tips,
> > +					      transport->server_options,
> > +					      transport->stateless_rpc,
> > +					      data->fd,
> > +					      data->options.acked_commits);
> > +			ret = 0;
> > +		}
> > +		goto cleanup;
> > +	}
> 
> These prereqs look right. This makes it look rather strange that
> negotiate_using_fetch() returns void (and has several die() calls inside)
> and could instead return an 'int' that is consumed here (and use
> error() calls instead of die()).

When negotiate_using_fetch() is used, we are already past the capability
advertisement step, so we need to believe here that the wait-for-done
prerequisite has been met. (Admittedly, said prerequisite wasn't
documented, but I've documented it following your suggestion above.) So
I think it would be too late to return an "int" after several
negotiation steps have occurred and the packfile downloaded.

> > +
> > +	/*
> > +	 * If set, whenever transport_fetch_refs() is called, add known common
> > +	 * commits to this oidset instead of fetching any packfiles.
> > +	 */
> > +	struct oidset *acked_commits;
> 
> nit: s/If set/If allocated/

Changed.

> > @@ -1668,10 +1673,13 @@ int upload_pack_v2(struct repository *r, struct strvec *keys,
> >  		case FETCH_PROCESS_ARGS:
> >  			process_args(request, &data);
> >  
> > -			if (!data.want_obj.nr) {
> > +			if (!data.want_obj.nr && !data.wait_for_done) {
> >  				/*
> > -				 * Request didn't contain any 'want' lines,
> > -				 * guess they didn't want anything.
> > +				 * Request didn't contain any 'want' lines (and
> > +				 * the request does not contain
> > +				 * "wait-for-done", in which it is reasonable
> > +				 * to just send 'have's without 'want's); guess
> > +				 * they didn't want anything.
> >  				 */
> >  				state = FETCH_DONE;
> >  			} else if (data.haves.nr) {
> > @@ -1723,7 +1731,7 @@ int upload_pack_advertise(struct repository *r,
> >  		int allow_sideband_all_value;
> >  		char *str = NULL;
> >  
> > -		strbuf_addstr(value, "shallow");
> > +		strbuf_addstr(value, "shallow wait-for-done");
> 
> It might be nice to have this wait-for-done capability configurable.
> I'd likely want this on by default, but in case there is an issue it
> is easier to change config values than ship new binaries.

I felt that we didn't need this knob on the server side as this doesn't
expose any more information than a regular fetch, but I'm open to adding
it if neeed be.

> This is a pretty big patch. It might have been nice to split the
> server-side stuff out as its own patch with a follow-up for the client
> code and the tests.
> 
> Thanks,
> -Stolee

Personally I prefer that such changes (server and client) be together,
so that I can see on both sides how things work. There is (in theory)
already a clear divide between both sides, even within a patch, since
the server and client parts are usually in different parts. But if the
majority prefers that such changes be separate, I'm OK with doing that
too.

Also, thanks for your review.

^ permalink raw reply	[flat|nested] 33+ messages in thread

* Re: [PATCH 6/6] send-pack: support push negotiation
  2021-05-03 15:35   ` Derrick Stolee
@ 2021-05-03 22:02     ` Jonathan Tan
  2021-05-04 17:26       ` Derrick Stolee
  0 siblings, 1 reply; 33+ messages in thread
From: Jonathan Tan @ 2021-05-03 22:02 UTC (permalink / raw)
  To: stolee; +Cc: jonathantanmy, git

[snip asking about whether extra_have (a.k.a. advertised) and commons (a.k.a.
negotiated) can be merged]

> Here, it would be nice if extra_have and commons were merged before calling
> pack_objects(). I mentioned a way to perhaps make that easier above, but
> the context might not make that be super-simple. Running a loop here to
> scan 'commons' and append them to 'extra_have' might be a sufficient
> approach.
> 
> Generally, this approach seems like it would work. I have not done any
> local testing, yet.
> 
> Thanks,
> -Stolee

I was reluctant to merge them because that would involve either (1)
adding commons to "extra_have" (as you suggest) or (2) iterating through
"extra_have" in order to add it to the "commons" set. For (1), this
would modify "extra_have", which is passed in from the outside. Looking
at its callers, the main one in git_transport_push() in transport.c
calls send_pack() with a set that has traversed the transport API, so I
think it would be confusing if such a set suddenly changed. For (2), the
extra loop seems more troublesome than having two parameters with
clearer names indicating where they come from. I don't mind changing to
(2), though, if people want it.

^ permalink raw reply	[flat|nested] 33+ messages in thread

* Re: [PATCH 6/6] send-pack: support push negotiation
  2021-05-03 22:02     ` Jonathan Tan
@ 2021-05-04 17:26       ` Derrick Stolee
  0 siblings, 0 replies; 33+ messages in thread
From: Derrick Stolee @ 2021-05-04 17:26 UTC (permalink / raw)
  To: Jonathan Tan; +Cc: git

On 5/3/2021 6:02 PM, Jonathan Tan wrote:
> [snip asking about whether extra_have (a.k.a. advertised) and commons (a.k.a.
> negotiated) can be merged]
> 
>> Here, it would be nice if extra_have and commons were merged before calling
>> pack_objects(). I mentioned a way to perhaps make that easier above, but
>> the context might not make that be super-simple. Running a loop here to
>> scan 'commons' and append them to 'extra_have' might be a sufficient
>> approach.
>>
>> Generally, this approach seems like it would work. I have not done any
>> local testing, yet.
>>
>> Thanks,
>> -Stolee
> 
> I was reluctant to merge them because that would involve either (1)
> adding commons to "extra_have" (as you suggest) or (2) iterating through
> "extra_have" in order to add it to the "commons" set. For (1), this
> would modify "extra_have", which is passed in from the outside. Looking
> at its callers, the main one in git_transport_push() in transport.c
> calls send_pack() with a set that has traversed the transport API, so I
> think it would be confusing if such a set suddenly changed. For (2), the
> extra loop seems more troublesome than having two parameters with
> clearer names indicating where they come from. I don't mind changing to
> (2), though, if people want it.
 
I suppose this concern about "ownership" is valid and worth having the
two parameters in the helper function for extra safety.

Thanks,
-Stolee

^ permalink raw reply	[flat|nested] 33+ messages in thread

* [PATCH v2 0/5] Push negotiation
  2021-04-09  1:09 [PATCH 0/6] Push negotiation Jonathan Tan
                   ` (6 preceding siblings ...)
  2021-04-30  5:42 ` [PATCH 0/6] Push negotiation Junio C Hamano
@ 2021-05-04 21:15 ` Jonathan Tan
  2021-05-04 21:15   ` [PATCH v2 1/5] fetch-pack: refactor process_acks() Jonathan Tan
                     ` (4 more replies)
  7 siblings, 5 replies; 33+ messages in thread
From: Jonathan Tan @ 2021-05-04 21:15 UTC (permalink / raw)
  To: git; +Cc: Jonathan Tan, gitster, stolee

Thanks for the review, Junio and Stolee.

The first patch in version 1 has been merged to master, I believe, so
here are the remaining 5 patches.

As Stolee pointed out, some tests in version 1 fail when
GIT_TEST_PROTOCOL_VERSION is set to 0. I have corrected that, but there
is one test that still fails in t5601. That seems to also fail in
"master". I'll see if I can fix it and send a separate patch for that.

Jonathan Tan (5):
  fetch-pack: refactor process_acks()
  fetch-pack: refactor add_haves()
  fetch-pack: refactor command and capability write
  fetch: teach independent negotiation (no packfile)
  send-pack: support push negotiation

 Documentation/config/push.txt           |   7 +
 Documentation/technical/protocol-v2.txt |   8 +
 builtin/fetch.c                         |  27 ++-
 fetch-pack.c                            | 246 ++++++++++++++++--------
 fetch-pack.h                            |  14 ++
 object.h                                |   2 +-
 send-pack.c                             |  61 +++++-
 t/t5516-fetch-push.sh                   |  35 ++++
 t/t5701-git-serve.sh                    |   2 +-
 t/t5702-protocol-v2.sh                  |  89 +++++++++
 transport-helper.c                      |  10 +
 transport.c                             |  30 ++-
 transport.h                             |   6 +
 upload-pack.c                           |  18 +-
 14 files changed, 455 insertions(+), 100 deletions(-)

Range-diff against v1:
-:  ---------- > 1:  8102570374 fetch-pack: refactor process_acks()
-:  ---------- > 2:  57c3451b2e fetch-pack: refactor add_haves()
-:  ---------- > 3:  6871d0cec6 fetch-pack: refactor command and capability write
1:  3ebe4ada28 ! 4:  1de34a6dce fetch: teach independent negotiation (no packfile)
    @@ Commit message
         There are 2 code paths that do not go through fetch_refs_via_pack() that
         needed to be individually excluded: the bundle transport (excluded
         through requiring smart_options, which the bundle transport doesn't
    -    support) and transport helpers that do not support takeover.
    -    Fortunately, none of these support protocol v2.
    +    support) and transport helpers that do not support takeover. If or when
    +    we support independent negotiation for protocol v0, we will need to
    +    modify these 2 code paths to support it. But for now, report failure if
    +    independent negotiation is requested in these cases.
     
         Signed-off-by: Jonathan Tan <jonathantanmy@google.com>
         Signed-off-by: Junio C Hamano <gitster@pobox.com>
    @@ builtin/fetch.c: int cmd_fetch(int argc, const char **argv, const char *prefix)
     +		const struct object_id *oid;
     +
     +		if (!remote)
    -+			die(_("Must supply remote when using --negotiate-only"));
    ++			die(_("must supply remote when using --negotiate-only"));
     +		gtransport = prepare_transport(remote, 1);
     +		if (gtransport->smart_options) {
     +			gtransport->smart_options->acked_commits = &acked_commits;
    @@ fetch-pack.c
      #include "fsck.h"
      #include "shallow.h"
     +#include "commit-reach.h"
    ++#include "commit-graph.h"
      
      static int transfer_unpack_limit = -1;
      static int fetch_unpack_limit = -1;
    @@ fetch-pack.c: struct ref *fetch_pack(struct fetch_pack_args *args,
     +{
     +	struct object_array *a = data;
     +
    -+	add_object_array(parse_object(the_repository, oid), "", a);
    ++	add_object_array(lookup_object(the_repository, oid), "", a);
     +	return 0;
     +}
     +
    ++static void clear_common_flag(struct oidset *s)
    ++{
    ++	struct oidset_iter iter;
    ++	const struct object_id *oid;
    ++	oidset_iter_init(s, &iter);
    ++
    ++	while ((oid = oidset_iter_next(&iter))) {
    ++		struct object *obj = lookup_object(the_repository, oid);
    ++		obj->flags &= ~COMMON;
    ++	}
    ++}
    ++
     +void negotiate_using_fetch(const struct oid_array *negotiation_tips,
     +			   const struct string_list *server_options,
     +			   int stateless_rpc,
    @@ fetch-pack.c: struct ref *fetch_pack(struct fetch_pack_args *args,
     +	int in_vain = 0;
     +	int seen_ack = 0;
     +	int last_iteration = 0;
    ++	timestamp_t min_generation = GENERATION_NUMBER_INFINITY;
     +
     +	fetch_negotiator_init(the_repository, &negotiator);
     +	mark_tips(&negotiator, negotiation_tips);
    @@ fetch-pack.c: struct ref *fetch_pack(struct fetch_pack_args *args,
     +				   &received_ready)) {
     +			struct commit *commit = lookup_commit(the_repository,
     +							      &common_oid);
    -+			if (commit)
    ++			if (commit) {
    ++				timestamp_t generation;
    ++
    ++				parse_commit_or_die(commit);
     +				commit->object.flags |= COMMON;
    ++				generation = commit_graph_generation(commit);
    ++				if (generation < min_generation)
    ++					min_generation = generation;
    ++			}
     +			in_vain = 0;
     +			seen_ack = 1;
     +			oidset_insert(acked_commits, &common_oid);
    @@ fetch-pack.c: struct ref *fetch_pack(struct fetch_pack_args *args,
     +			do_check_stateless_delimiter(stateless_rpc, &reader);
     +		if (can_all_from_reach_with_flag(&nt_object_array, COMMON,
     +						 REACH_SCRATCH, 0,
    -+						 GENERATION_NUMBER_ZERO))
    ++						 min_generation))
     +			last_iteration = 1;
     +	}
    ++	clear_common_flag(acked_commits);
     +	strbuf_release(&req_buf);
     +}
     +
    @@ fetch-pack.h: struct ref *fetch_pack(struct fetch_pack_args *args,
     +/*
     + * Execute the --negotiate-only mode of "git fetch", adding all known common
     + * commits to acked_commits.
    ++ *
    ++ * In the capability advertisement that has happened prior to invoking this
    ++ * function, the "wait-for-done" capability must be present.
     + */
     +void negotiate_using_fetch(const struct oid_array *negotiation_tips,
     +			   const struct string_list *server_options,
    @@ t/t5702-protocol-v2.sh: test_expect_success 'deepen-relative' '
     +
     +	setup_negotiate_only "$SERVER" "$URI" &&
     +
    -+	git -C client fetch \
    ++	git -c protocol.version=2 -C client fetch \
     +		--no-tags \
     +		--negotiate-only \
     +		--negotiation-tip=$(git -C client rev-parse HEAD) \
    @@ t/t5702-protocol-v2.sh: test_expect_success 'packfile-uri with transfer.fsckobje
     +
     +	setup_negotiate_only "$SERVER" "$URI" &&
     +
    -+	git -C client fetch \
    ++	git -c protocol.version=2 -C client fetch \
     +		--no-tags \
     +		--negotiate-only \
     +		--negotiation-tip=$(git -C client rev-parse HEAD) \
    @@ t/t5702-protocol-v2.sh: test_expect_success 'packfile-uri with transfer.fsckobje
     +	echo "s/ wait-for-done/ xxxx-xxx-xxxx/" \
     +		>"$HTTPD_ROOT_PATH/one-time-perl" &&
     +
    -+	test_must_fail git -C client fetch \
    ++	test_must_fail git -c protocol.version=2 -C client fetch \
     +		--no-tags \
     +		--negotiate-only \
     +		--negotiation-tip=$(git -C client rev-parse HEAD) \
    @@ transport.h: struct git_transport_options {
      	struct oid_array *negotiation_tips;
     +
     +	/*
    -+	 * If set, whenever transport_fetch_refs() is called, add known common
    -+	 * commits to this oidset instead of fetching any packfiles.
    ++	 * If allocated, whenever transport_fetch_refs() is called, add known
    ++	 * common commits to this oidset instead of fetching any packfiles.
     +	 */
     +	struct oidset *acked_commits;
      };
2:  bd55d6ba36 ! 5:  d38a8b7d66 send-pack: support push negotiation
    @@ t/t5516-fetch-push.sh: test_expect_success 'fetch with pushInsteadOf (should not
     +	git push testrepo $the_first_commit:refs/remotes/origin/first_commit &&
     +	git -C testrepo config receive.hideRefs refs/remotes/origin/first_commit &&
     +	echo now pushing without negotiation &&
    -+	GIT_TRACE2_EVENT="$(pwd)/event" git push testrepo refs/heads/main:refs/remotes/origin/main &&
    ++	GIT_TRACE2_EVENT="$(pwd)/event" git -c protocol.version=2 push testrepo refs/heads/main:refs/remotes/origin/main &&
     +	grep_wrote 5 event && # 2 commits, 2 trees, 1 blob
     +
     +	# Same commands, but with negotiation
    @@ t/t5516-fetch-push.sh: test_expect_success 'fetch with pushInsteadOf (should not
     +	mk_empty testrepo &&
     +	git push testrepo $the_first_commit:refs/remotes/origin/first_commit &&
     +	git -C testrepo config receive.hideRefs refs/remotes/origin/first_commit &&
    -+	GIT_TRACE2_EVENT="$(pwd)/event" git -c push.negotiate=1 push testrepo refs/heads/main:refs/remotes/origin/main &&
    ++	GIT_TRACE2_EVENT="$(pwd)/event" git -c protocol.version=2 -c push.negotiate=1 push testrepo refs/heads/main:refs/remotes/origin/main &&
     +	grep_wrote 2 event # 1 commit, 1 tree
     +'
     +
    @@ t/t5516-fetch-push.sh: test_expect_success 'fetch with pushInsteadOf (should not
     +	mk_empty testrepo &&
     +	git push testrepo $the_first_commit:refs/remotes/origin/first_commit &&
     +	git -C testrepo config receive.hideRefs refs/remotes/origin/first_commit &&
    -+	GIT_TRACE_PACKET="$(pwd)/trace" GIT_TEST_PROTOCOL_VERSION=0 GIT_TRACE2_EVENT="$(pwd)/event" \
    ++	GIT_TEST_PROTOCOL_VERSION=0 GIT_TRACE2_EVENT="$(pwd)/event" \
     +		git -c push.negotiate=1 push testrepo refs/heads/main:refs/remotes/origin/main 2>err &&
     +	grep_wrote 5 event && # 2 commits, 2 trees, 1 blob
     +	test_i18ngrep "push negotiation failed" err
-- 
2.31.1.527.g47e6f16901-goog


^ permalink raw reply	[flat|nested] 33+ messages in thread

* [PATCH v2 1/5] fetch-pack: refactor process_acks()
  2021-05-04 21:15 ` [PATCH v2 0/5] " Jonathan Tan
@ 2021-05-04 21:15   ` Jonathan Tan
  2021-05-04 21:15   ` [PATCH v2 2/5] fetch-pack: refactor add_haves() Jonathan Tan
                     ` (3 subsequent siblings)
  4 siblings, 0 replies; 33+ messages in thread
From: Jonathan Tan @ 2021-05-04 21:15 UTC (permalink / raw)
  To: git; +Cc: Jonathan Tan, gitster, stolee

A subsequent commit will need part, but not all, of the functionality in
process_acks(), so move some of its functionality to its sole caller
do_fetch_pack_v2(). As a side effect, the resulting code is also
shorter.

Signed-off-by: Jonathan Tan <jonathantanmy@google.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
---
 fetch-pack.c | 70 +++++++++++++++++-----------------------------------
 1 file changed, 22 insertions(+), 48 deletions(-)

diff --git a/fetch-pack.c b/fetch-pack.c
index 2318ebe680..9f3901cdba 100644
--- a/fetch-pack.c
+++ b/fetch-pack.c
@@ -1351,35 +1351,11 @@ static int process_section_header(struct packet_reader *reader,
 	return ret;
 }
 
-enum common_found {
-	/*
-	 * No commit was found to be possessed by both the client and the
-	 * server, and "ready" was not received.
-	 */
-	NO_COMMON_FOUND,
-
-	/*
-	 * At least one commit was found to be possessed by both the client and
-	 * the server, and "ready" was not received.
-	 */
-	COMMON_FOUND,
-
-	/*
-	 * "ready" was received, indicating that the server is ready to send
-	 * the packfile without any further negotiation.
-	 */
-	READY
-};
-
-static enum common_found process_acks(struct fetch_negotiator *negotiator,
-				      struct packet_reader *reader,
-				      struct oidset *common)
+static int process_ack(struct fetch_negotiator *negotiator,
+		       struct packet_reader *reader,
+		       struct object_id *common_oid,
+		       int *received_ready)
 {
-	/* received */
-	int received_ready = 0;
-	int received_ack = 0;
-
-	process_section_header(reader, "acknowledgments", 0);
 	while (packet_reader_read(reader) == PACKET_READ_NORMAL) {
 		const char *arg;
 
@@ -1387,20 +1363,17 @@ static enum common_found process_acks(struct fetch_negotiator *negotiator,
 			continue;
 
 		if (skip_prefix(reader->line, "ACK ", &arg)) {
-			struct object_id oid;
-			received_ack = 1;
-			if (!get_oid_hex(arg, &oid)) {
+			if (!get_oid_hex(arg, common_oid)) {
 				struct commit *commit;
-				oidset_insert(common, &oid);
-				commit = lookup_commit(the_repository, &oid);
+				commit = lookup_commit(the_repository, common_oid);
 				if (negotiator)
 					negotiator->ack(negotiator, commit);
 			}
-			continue;
+			return 1;
 		}
 
 		if (!strcmp(reader->line, "ready")) {
-			received_ready = 1;
+			*received_ready = 1;
 			continue;
 		}
 
@@ -1418,13 +1391,12 @@ static enum common_found process_acks(struct fetch_negotiator *negotiator,
 	 * sent. Therefore, a DELIM is expected if "ready" is sent, and a FLUSH
 	 * otherwise.
 	 */
-	if (received_ready && reader->status != PACKET_READ_DELIM)
+	if (*received_ready && reader->status != PACKET_READ_DELIM)
 		die(_("expected packfile to be sent after 'ready'"));
-	if (!received_ready && reader->status != PACKET_READ_FLUSH)
+	if (!*received_ready && reader->status != PACKET_READ_FLUSH)
 		die(_("expected no other sections to be sent after no 'ready'"));
 
-	return received_ready ? READY :
-		(received_ack ? COMMON_FOUND : NO_COMMON_FOUND);
+	return 0;
 }
 
 static void receive_shallow_info(struct fetch_pack_args *args,
@@ -1573,6 +1545,8 @@ static struct ref *do_fetch_pack_v2(struct fetch_pack_args *args,
 	struct fetch_negotiator negotiator_alloc;
 	struct fetch_negotiator *negotiator;
 	int seen_ack = 0;
+	struct object_id common_oid;
+	int received_ready = 0;
 	struct string_list packfile_uris = STRING_LIST_INIT_DUP;
 	int i;
 	struct strvec index_pack_args = STRVEC_INIT;
@@ -1631,22 +1605,22 @@ static struct ref *do_fetch_pack_v2(struct fetch_pack_args *args,
 			break;
 		case FETCH_PROCESS_ACKS:
 			/* Process ACKs/NAKs */
-			switch (process_acks(negotiator, &reader, &common)) {
-			case READY:
+			process_section_header(&reader, "acknowledgments", 0);
+			while (process_ack(negotiator, &reader, &common_oid,
+					   &received_ready)) {
+				in_vain = 0;
+				seen_ack = 1;
+				oidset_insert(&common, &common_oid);
+			}
+			if (received_ready) {
 				/*
 				 * Don't check for response delimiter; get_pack() will
 				 * read the rest of this response.
 				 */
 				state = FETCH_GET_PACK;
-				break;
-			case COMMON_FOUND:
-				in_vain = 0;
-				seen_ack = 1;
-				/* fallthrough */
-			case NO_COMMON_FOUND:
+			} else {
 				do_check_stateless_delimiter(args, &reader);
 				state = FETCH_SEND_REQUEST;
-				break;
 			}
 			break;
 		case FETCH_GET_PACK:
-- 
2.31.1.527.g47e6f16901-goog


^ permalink raw reply	[flat|nested] 33+ messages in thread

* [PATCH v2 2/5] fetch-pack: refactor add_haves()
  2021-05-04 21:15 ` [PATCH v2 0/5] " Jonathan Tan
  2021-05-04 21:15   ` [PATCH v2 1/5] fetch-pack: refactor process_acks() Jonathan Tan
@ 2021-05-04 21:15   ` Jonathan Tan
  2021-05-04 21:16   ` [PATCH v2 3/5] fetch-pack: refactor command and capability write Jonathan Tan
                     ` (2 subsequent siblings)
  4 siblings, 0 replies; 33+ messages in thread
From: Jonathan Tan @ 2021-05-04 21:15 UTC (permalink / raw)
  To: git; +Cc: Jonathan Tan, gitster, stolee

A subsequent commit will need part, but not all, of the functionality in
add_haves(), so move some of its functionality to its sole caller
send_fetch_request().

Signed-off-by: Jonathan Tan <jonathantanmy@google.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
---
 fetch-pack.c | 28 ++++++++++++----------------
 1 file changed, 12 insertions(+), 16 deletions(-)

diff --git a/fetch-pack.c b/fetch-pack.c
index 9f3901cdba..128ad47d2a 100644
--- a/fetch-pack.c
+++ b/fetch-pack.c
@@ -1195,11 +1195,9 @@ static void add_common(struct strbuf *req_buf, struct oidset *common)
 }
 
 static int add_haves(struct fetch_negotiator *negotiator,
-		     int seen_ack,
 		     struct strbuf *req_buf,
-		     int *haves_to_send, int *in_vain)
+		     int *haves_to_send)
 {
-	int ret = 0;
 	int haves_added = 0;
 	const struct object_id *oid;
 
@@ -1209,17 +1207,10 @@ static int add_haves(struct fetch_negotiator *negotiator,
 			break;
 	}
 
-	*in_vain += haves_added;
-	if (!haves_added || (seen_ack && *in_vain >= MAX_IN_VAIN)) {
-		/* Send Done */
-		packet_buf_write(req_buf, "done\n");
-		ret = 1;
-	}
-
 	/* Increase haves to send on next round */
 	*haves_to_send = next_flush(1, *haves_to_send);
 
-	return ret;
+	return haves_added;
 }
 
 static int send_fetch_request(struct fetch_negotiator *negotiator, int fd_out,
@@ -1228,7 +1219,8 @@ static int send_fetch_request(struct fetch_negotiator *negotiator, int fd_out,
 			      int *haves_to_send, int *in_vain,
 			      int sideband_all, int seen_ack)
 {
-	int ret = 0;
+	int haves_added;
+	int done_sent = 0;
 	const char *hash_name;
 	struct strbuf req_buf = STRBUF_INIT;
 
@@ -1312,9 +1304,13 @@ static int send_fetch_request(struct fetch_negotiator *negotiator, int fd_out,
 	/* Add all of the common commits we've found in previous rounds */
 	add_common(&req_buf, common);
 
-	/* Add initial haves */
-	ret = add_haves(negotiator, seen_ack, &req_buf,
-			haves_to_send, in_vain);
+	haves_added = add_haves(negotiator, &req_buf, haves_to_send);
+	*in_vain += haves_added;
+	if (!haves_added || (seen_ack && *in_vain >= MAX_IN_VAIN)) {
+		/* Send Done */
+		packet_buf_write(&req_buf, "done\n");
+		done_sent = 1;
+	}
 
 	/* Send request */
 	packet_buf_flush(&req_buf);
@@ -1322,7 +1318,7 @@ static int send_fetch_request(struct fetch_negotiator *negotiator, int fd_out,
 		die_errno(_("unable to write request to remote"));
 
 	strbuf_release(&req_buf);
-	return ret;
+	return done_sent;
 }
 
 /*
-- 
2.31.1.527.g47e6f16901-goog


^ permalink raw reply	[flat|nested] 33+ messages in thread

* [PATCH v2 3/5] fetch-pack: refactor command and capability write
  2021-05-04 21:15 ` [PATCH v2 0/5] " Jonathan Tan
  2021-05-04 21:15   ` [PATCH v2 1/5] fetch-pack: refactor process_acks() Jonathan Tan
  2021-05-04 21:15   ` [PATCH v2 2/5] fetch-pack: refactor add_haves() Jonathan Tan
@ 2021-05-04 21:16   ` Jonathan Tan
  2021-05-04 21:16   ` [PATCH v2 4/5] fetch: teach independent negotiation (no packfile) Jonathan Tan
  2021-05-04 21:16   ` [PATCH v2 5/5] send-pack: support push negotiation Jonathan Tan
  4 siblings, 0 replies; 33+ messages in thread
From: Jonathan Tan @ 2021-05-04 21:16 UTC (permalink / raw)
  To: git; +Cc: Jonathan Tan, gitster, stolee

A subsequent commit will need this functionality independent of the rest
of send_fetch_request(), so put this into its own function.

Signed-off-by: Jonathan Tan <jonathantanmy@google.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
---
 fetch-pack.c | 41 ++++++++++++++++++++++++-----------------
 1 file changed, 24 insertions(+), 17 deletions(-)

diff --git a/fetch-pack.c b/fetch-pack.c
index 128ad47d2a..512fe5450d 100644
--- a/fetch-pack.c
+++ b/fetch-pack.c
@@ -1213,29 +1213,23 @@ static int add_haves(struct fetch_negotiator *negotiator,
 	return haves_added;
 }
 
-static int send_fetch_request(struct fetch_negotiator *negotiator, int fd_out,
-			      struct fetch_pack_args *args,
-			      const struct ref *wants, struct oidset *common,
-			      int *haves_to_send, int *in_vain,
-			      int sideband_all, int seen_ack)
+static void write_fetch_command_and_capabilities(struct strbuf *req_buf,
+						 const struct string_list *server_options)
 {
-	int haves_added;
-	int done_sent = 0;
 	const char *hash_name;
-	struct strbuf req_buf = STRBUF_INIT;
 
 	if (server_supports_v2("fetch", 1))
-		packet_buf_write(&req_buf, "command=fetch");
+		packet_buf_write(req_buf, "command=fetch");
 	if (server_supports_v2("agent", 0))
-		packet_buf_write(&req_buf, "agent=%s", git_user_agent_sanitized());
+		packet_buf_write(req_buf, "agent=%s", git_user_agent_sanitized());
 	if (advertise_sid && server_supports_v2("session-id", 0))
-		packet_buf_write(&req_buf, "session-id=%s", trace2_session_id());
-	if (args->server_options && args->server_options->nr &&
+		packet_buf_write(req_buf, "session-id=%s", trace2_session_id());
+	if (server_options && server_options->nr &&
 	    server_supports_v2("server-option", 1)) {
 		int i;
-		for (i = 0; i < args->server_options->nr; i++)
-			packet_buf_write(&req_buf, "server-option=%s",
-					 args->server_options->items[i].string);
+		for (i = 0; i < server_options->nr; i++)
+			packet_buf_write(req_buf, "server-option=%s",
+					 server_options->items[i].string);
 	}
 
 	if (server_feature_v2("object-format", &hash_name)) {
@@ -1243,13 +1237,26 @@ static int send_fetch_request(struct fetch_negotiator *negotiator, int fd_out,
 		if (hash_algo_by_ptr(the_hash_algo) != hash_algo)
 			die(_("mismatched algorithms: client %s; server %s"),
 			    the_hash_algo->name, hash_name);
-		packet_buf_write(&req_buf, "object-format=%s", the_hash_algo->name);
+		packet_buf_write(req_buf, "object-format=%s", the_hash_algo->name);
 	} else if (hash_algo_by_ptr(the_hash_algo) != GIT_HASH_SHA1) {
 		die(_("the server does not support algorithm '%s'"),
 		    the_hash_algo->name);
 	}
+	packet_buf_delim(req_buf);
+}
+
+static int send_fetch_request(struct fetch_negotiator *negotiator, int fd_out,
+			      struct fetch_pack_args *args,
+			      const struct ref *wants, struct oidset *common,
+			      int *haves_to_send, int *in_vain,
+			      int sideband_all, int seen_ack)
+{
+	int haves_added;
+	int done_sent = 0;
+	struct strbuf req_buf = STRBUF_INIT;
+
+	write_fetch_command_and_capabilities(&req_buf, args->server_options);
 
-	packet_buf_delim(&req_buf);
 	if (args->use_thin_pack)
 		packet_buf_write(&req_buf, "thin-pack");
 	if (args->no_progress)
-- 
2.31.1.527.g47e6f16901-goog


^ permalink raw reply	[flat|nested] 33+ messages in thread

* [PATCH v2 4/5] fetch: teach independent negotiation (no packfile)
  2021-05-04 21:15 ` [PATCH v2 0/5] " Jonathan Tan
                     ` (2 preceding siblings ...)
  2021-05-04 21:16   ` [PATCH v2 3/5] fetch-pack: refactor command and capability write Jonathan Tan
@ 2021-05-04 21:16   ` Jonathan Tan
  2021-05-05  1:53     ` Junio C Hamano
  2021-05-05 16:44     ` Derrick Stolee
  2021-05-04 21:16   ` [PATCH v2 5/5] send-pack: support push negotiation Jonathan Tan
  4 siblings, 2 replies; 33+ messages in thread
From: Jonathan Tan @ 2021-05-04 21:16 UTC (permalink / raw)
  To: git; +Cc: Jonathan Tan, gitster, stolee

Currently, the packfile negotiation step within a Git fetch cannot be
done independent of sending the packfile, even though there is at least
one application wherein this is useful. Therefore, make it possible for
this negotiation step to be done independently. A subsequent commit will
use this for one such application - push negotiation.

This feature is for protocol v2 only. (An implementation for protocol v0
would require a separate implementation in the fetch, transport, and
transport helper code.)

In the protocol, the main hindrance towards independent negotiation is
that the server can unilaterally decide to send the packfile. This is
solved by a "wait-for-done" argument: the server will then wait for the
client to say "done". In practice, the client will never say it; instead
it will cease requests once it is satisfied.

In the client, the main change lies in the transport and transport
helper code. fetch_refs_via_pack() performs everything needed - protocol
version and capability checks, and the negotiation itself.

There are 2 code paths that do not go through fetch_refs_via_pack() that
needed to be individually excluded: the bundle transport (excluded
through requiring smart_options, which the bundle transport doesn't
support) and transport helpers that do not support takeover. If or when
we support independent negotiation for protocol v0, we will need to
modify these 2 code paths to support it. But for now, report failure if
independent negotiation is requested in these cases.

Signed-off-by: Jonathan Tan <jonathantanmy@google.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
---
 Documentation/technical/protocol-v2.txt |   8 ++
 builtin/fetch.c                         |  27 +++++-
 fetch-pack.c                            | 111 +++++++++++++++++++++++-
 fetch-pack.h                            |  14 +++
 object.h                                |   2 +-
 t/t5701-git-serve.sh                    |   2 +-
 t/t5702-protocol-v2.sh                  |  89 +++++++++++++++++++
 transport-helper.c                      |  10 +++
 transport.c                             |  30 +++++--
 transport.h                             |   6 ++
 upload-pack.c                           |  18 ++--
 11 files changed, 300 insertions(+), 17 deletions(-)

diff --git a/Documentation/technical/protocol-v2.txt b/Documentation/technical/protocol-v2.txt
index a7c806a73e..0b371d8de4 100644
--- a/Documentation/technical/protocol-v2.txt
+++ b/Documentation/technical/protocol-v2.txt
@@ -346,6 +346,14 @@ explained below.
 	client should download from all given URIs. Currently, the
 	protocols supported are "http" and "https".
 
+If the 'wait-for-done' feature is advertised, the following argument
+can be included in the client's request.
+
+    wait-for-done
+	Indicates to the server that it should never send "ready", but
+	should wait for the client to say "done" before sending the
+	packfile.
+
 The response of `fetch` is broken into a number of sections separated by
 delimiter packets (0001), with each section beginning with its section
 header. Most sections are sent only when the packfile is sent.
diff --git a/builtin/fetch.c b/builtin/fetch.c
index 0b90de87c7..a732295a6b 100644
--- a/builtin/fetch.c
+++ b/builtin/fetch.c
@@ -82,6 +82,7 @@ static struct string_list server_options = STRING_LIST_INIT_DUP;
 static struct string_list negotiation_tip = STRING_LIST_INIT_NODUP;
 static int fetch_write_commit_graph = -1;
 static int stdin_refspecs = 0;
+static int negotiate_only;
 
 static int git_fetch_config(const char *k, const char *v, void *cb)
 {
@@ -202,6 +203,8 @@ static struct option builtin_fetch_options[] = {
 			TRANSPORT_FAMILY_IPV6),
 	OPT_STRING_LIST(0, "negotiation-tip", &negotiation_tip, N_("revision"),
 			N_("report that we have only objects reachable from this object")),
+	OPT_BOOL(0, "negotiate-only", &negotiate_only,
+		 N_("do not fetch a packfile; instead, print ancestors of negotiation tips")),
 	OPT_PARSE_LIST_OBJECTS_FILTER(&filter_options),
 	OPT_BOOL(0, "auto-maintenance", &enable_auto_gc,
 		 N_("run 'maintenance --auto' after fetching")),
@@ -1986,7 +1989,29 @@ int cmd_fetch(int argc, const char **argv, const char *prefix)
 		}
 	}
 
-	if (remote) {
+	if (negotiate_only) {
+		struct oidset acked_commits = OIDSET_INIT;
+		struct oidset_iter iter;
+		const struct object_id *oid;
+
+		if (!remote)
+			die(_("must supply remote when using --negotiate-only"));
+		gtransport = prepare_transport(remote, 1);
+		if (gtransport->smart_options) {
+			gtransport->smart_options->acked_commits = &acked_commits;
+		} else {
+			warning(_("Protocol does not support --negotiate-only, exiting."));
+			return 1;
+		}
+		if (server_options.nr)
+			gtransport->server_options = &server_options;
+		result = transport_fetch_refs(gtransport, NULL);
+
+		oidset_iter_init(&acked_commits, &iter);
+		while ((oid = oidset_iter_next(&iter)))
+			printf("%s\n", oid_to_hex(oid));
+		oidset_clear(&acked_commits);
+	} else if (remote) {
 		if (filter_options.choice || has_promisor_remote())
 			fetch_one_setup_partial(remote);
 		result = fetch_one(remote, argc, argv, prune_tags_ok, stdin_refspecs);
diff --git a/fetch-pack.c b/fetch-pack.c
index 512fe5450d..c135635e34 100644
--- a/fetch-pack.c
+++ b/fetch-pack.c
@@ -23,6 +23,8 @@
 #include "fetch-negotiator.h"
 #include "fsck.h"
 #include "shallow.h"
+#include "commit-reach.h"
+#include "commit-graph.h"
 
 static int transfer_unpack_limit = -1;
 static int fetch_unpack_limit = -1;
@@ -45,6 +47,8 @@ static struct string_list uri_protocols = STRING_LIST_INIT_DUP;
 /* Remember to update object flag allocation in object.h */
 #define COMPLETE	(1U << 0)
 #define ALTERNATE	(1U << 1)
+#define COMMON		(1U << 6)
+#define REACH_SCRATCH	(1U << 7)
 
 /*
  * After sending this many "have"s if we do not get any new ACK , we
@@ -1523,10 +1527,10 @@ enum fetch_state {
 	FETCH_DONE,
 };
 
-static void do_check_stateless_delimiter(const struct fetch_pack_args *args,
+static void do_check_stateless_delimiter(int stateless_rpc,
 					 struct packet_reader *reader)
 {
-	check_stateless_delimiter(args->stateless_rpc, reader,
+	check_stateless_delimiter(stateless_rpc, reader,
 				  _("git fetch-pack: expected response end packet"));
 }
 
@@ -1622,7 +1626,7 @@ static struct ref *do_fetch_pack_v2(struct fetch_pack_args *args,
 				 */
 				state = FETCH_GET_PACK;
 			} else {
-				do_check_stateless_delimiter(args, &reader);
+				do_check_stateless_delimiter(args->stateless_rpc, &reader);
 				state = FETCH_SEND_REQUEST;
 			}
 			break;
@@ -1645,7 +1649,7 @@ static struct ref *do_fetch_pack_v2(struct fetch_pack_args *args,
 				     packfile_uris.nr ? &index_pack_args : NULL,
 				     sought, nr_sought, &fsck_options.gitmodules_found))
 				die(_("git fetch-pack: fetch failed."));
-			do_check_stateless_delimiter(args, &reader);
+			do_check_stateless_delimiter(args->stateless_rpc, &reader);
 
 			state = FETCH_DONE;
 			break;
@@ -1962,6 +1966,105 @@ struct ref *fetch_pack(struct fetch_pack_args *args,
 	return ref_cpy;
 }
 
+static int add_to_object_array(const struct object_id *oid, void *data)
+{
+	struct object_array *a = data;
+
+	add_object_array(lookup_object(the_repository, oid), "", a);
+	return 0;
+}
+
+static void clear_common_flag(struct oidset *s)
+{
+	struct oidset_iter iter;
+	const struct object_id *oid;
+	oidset_iter_init(s, &iter);
+
+	while ((oid = oidset_iter_next(&iter))) {
+		struct object *obj = lookup_object(the_repository, oid);
+		obj->flags &= ~COMMON;
+	}
+}
+
+void negotiate_using_fetch(const struct oid_array *negotiation_tips,
+			   const struct string_list *server_options,
+			   int stateless_rpc,
+			   int fd[],
+			   struct oidset *acked_commits)
+{
+	struct fetch_negotiator negotiator;
+	struct packet_reader reader;
+	struct object_array nt_object_array = OBJECT_ARRAY_INIT;
+	struct strbuf req_buf = STRBUF_INIT;
+	int haves_to_send = INITIAL_FLUSH;
+	int in_vain = 0;
+	int seen_ack = 0;
+	int last_iteration = 0;
+	timestamp_t min_generation = GENERATION_NUMBER_INFINITY;
+
+	fetch_negotiator_init(the_repository, &negotiator);
+	mark_tips(&negotiator, negotiation_tips);
+
+	packet_reader_init(&reader, fd[0], NULL, 0,
+			   PACKET_READ_CHOMP_NEWLINE |
+			   PACKET_READ_DIE_ON_ERR_PACKET);
+
+	oid_array_for_each((struct oid_array *) negotiation_tips,
+			   add_to_object_array,
+			   &nt_object_array);
+
+	while (!last_iteration) {
+		int haves_added;
+		struct object_id common_oid;
+		int received_ready = 0;
+
+		strbuf_reset(&req_buf);
+		write_fetch_command_and_capabilities(&req_buf, server_options);
+
+		packet_buf_write(&req_buf, "wait-for-done");
+
+		haves_added = add_haves(&negotiator, &req_buf, &haves_to_send);
+		in_vain += haves_added;
+		if (!haves_added || (seen_ack && in_vain >= MAX_IN_VAIN))
+			last_iteration = 1;
+
+		/* Send request */
+		packet_buf_flush(&req_buf);
+		if (write_in_full(fd[1], req_buf.buf, req_buf.len) < 0)
+			die_errno(_("unable to write request to remote"));
+
+		/* Process ACKs/NAKs */
+		process_section_header(&reader, "acknowledgments", 0);
+		while (process_ack(&negotiator, &reader, &common_oid,
+				   &received_ready)) {
+			struct commit *commit = lookup_commit(the_repository,
+							      &common_oid);
+			if (commit) {
+				timestamp_t generation;
+
+				parse_commit_or_die(commit);
+				commit->object.flags |= COMMON;
+				generation = commit_graph_generation(commit);
+				if (generation < min_generation)
+					min_generation = generation;
+			}
+			in_vain = 0;
+			seen_ack = 1;
+			oidset_insert(acked_commits, &common_oid);
+		}
+		if (received_ready)
+			die(_("unexpected 'ready' from remote"));
+		else
+			do_check_stateless_delimiter(stateless_rpc, &reader);
+		if (can_all_from_reach_with_flag(&nt_object_array, COMMON,
+						 REACH_SCRATCH, 0,
+						 min_generation))
+			last_iteration = 1;
+	}
+	clear_common_flag(acked_commits);
+	strbuf_release(&req_buf);
+}
+
 int report_unmatched_refs(struct ref **sought, int nr_sought)
 {
 	int i, ret = 0;
diff --git a/fetch-pack.h b/fetch-pack.h
index f114d72775..7f94a2a583 100644
--- a/fetch-pack.h
+++ b/fetch-pack.h
@@ -5,6 +5,7 @@
 #include "run-command.h"
 #include "protocol.h"
 #include "list-objects-filter-options.h"
+#include "oidset.h"
 
 struct oid_array;
 
@@ -81,6 +82,19 @@ struct ref *fetch_pack(struct fetch_pack_args *args,
 		       struct string_list *pack_lockfiles,
 		       enum protocol_version version);
 
+/*
+ * Execute the --negotiate-only mode of "git fetch", adding all known common
+ * commits to acked_commits.
+ *
+ * In the capability advertisement that has happened prior to invoking this
+ * function, the "wait-for-done" capability must be present.
+ */
+void negotiate_using_fetch(const struct oid_array *negotiation_tips,
+			   const struct string_list *server_options,
+			   int stateless_rpc,
+			   int fd[],
+			   struct oidset *acked_commits);
+
 /*
  * Print an appropriate error message for each sought ref that wasn't
  * matched.  Return 0 if all sought refs were matched, otherwise 1.
diff --git a/object.h b/object.h
index 59daadce21..4806fa8e66 100644
--- a/object.h
+++ b/object.h
@@ -60,7 +60,7 @@ struct object_array {
 /*
  * object flag allocation:
  * revision.h:               0---------10         15             23------26
- * fetch-pack.c:             01
+ * fetch-pack.c:             01    67
  * negotiator/default.c:       2--5
  * walker.c:                 0-2
  * upload-pack.c:                4       11-----14  16-----19
diff --git a/t/t5701-git-serve.sh b/t/t5701-git-serve.sh
index 509f379d49..f03bb04803 100755
--- a/t/t5701-git-serve.sh
+++ b/t/t5701-git-serve.sh
@@ -16,7 +16,7 @@ test_expect_success 'test capability advertisement' '
 	version 2
 	agent=git/$(git version | cut -d" " -f3)
 	ls-refs=unborn
-	fetch=shallow
+	fetch=shallow wait-for-done
 	server-option
 	object-format=$(test_oid algo)
 	0000
diff --git a/t/t5702-protocol-v2.sh b/t/t5702-protocol-v2.sh
index 2e1243ca40..66af411057 100755
--- a/t/t5702-protocol-v2.sh
+++ b/t/t5702-protocol-v2.sh
@@ -585,6 +585,49 @@ test_expect_success 'deepen-relative' '
 	test_cmp expected actual
 '
 
+setup_negotiate_only () {
+	SERVER="$1"
+	URI="$2"
+
+	rm -rf "$SERVER" client
+
+	git init "$SERVER"
+	test_commit -C "$SERVER" one
+	test_commit -C "$SERVER" two
+
+	git clone "$URI" client
+	test_commit -C client three
+}
+
+test_expect_success 'file:// --negotiate-only' '
+	SERVER="server" &&
+	URI="file://$(pwd)/server" &&
+
+	setup_negotiate_only "$SERVER" "$URI" &&
+
+	git -c protocol.version=2 -C client fetch \
+		--no-tags \
+		--negotiate-only \
+		--negotiation-tip=$(git -C client rev-parse HEAD) \
+		origin >out &&
+	COMMON=$(git -C "$SERVER" rev-parse two) &&
+	grep "$COMMON" out
+'
+
+test_expect_success 'file:// --negotiate-only with protocol v0' '
+	SERVER="server" &&
+	URI="file://$(pwd)/server" &&
+
+	setup_negotiate_only "$SERVER" "$URI" &&
+
+	test_must_fail git -c protocol.version=0 -C client fetch \
+		--no-tags \
+		--negotiate-only \
+		--negotiation-tip=$(git -C client rev-parse HEAD) \
+		origin 2>err &&
+	test_i18ngrep "negotiate-only requires protocol v2" err
+'
+
 # Test protocol v2 with 'http://' transport
 #
 . "$TEST_DIRECTORY"/lib-httpd.sh
@@ -1035,6 +1078,52 @@ test_expect_success 'packfile-uri with transfer.fsckobjects fails when .gitmodul
 	test_i18ngrep "disallowed submodule name" err
 '
 
+test_expect_success 'http:// --negotiate-only' '
+	SERVER="$HTTPD_DOCUMENT_ROOT_PATH/server" &&
+	URI="$HTTPD_URL/smart/server" &&
+
+	setup_negotiate_only "$SERVER" "$URI" &&
+
+	git -c protocol.version=2 -C client fetch \
+		--no-tags \
+		--negotiate-only \
+		--negotiation-tip=$(git -C client rev-parse HEAD) \
+		origin >out &&
+	COMMON=$(git -C "$SERVER" rev-parse two) &&
+	grep "$COMMON" out
+'
+
+test_expect_success 'http:// --negotiate-only without wait-for-done support' '
+	SERVER="server" &&
+	URI="$HTTPD_URL/one_time_perl/server" &&
+
+	setup_negotiate_only "$SERVER" "$URI" &&
+
+	echo "s/ wait-for-done/ xxxx-xxx-xxxx/" \
+		>"$HTTPD_ROOT_PATH/one-time-perl" &&
+
+	test_must_fail git -c protocol.version=2 -C client fetch \
+		--no-tags \
+		--negotiate-only \
+		--negotiation-tip=$(git -C client rev-parse HEAD) \
+		origin 2>err &&
+	test_i18ngrep "server does not support wait-for-done" err
+'
+
+test_expect_success 'http:// --negotiate-only with protocol v0' '
+	SERVER="$HTTPD_DOCUMENT_ROOT_PATH/server" &&
+	URI="$HTTPD_URL/smart/server" &&
+
+	setup_negotiate_only "$SERVER" "$URI" &&
+
+	test_must_fail git -c protocol.version=0 -C client fetch \
+		--no-tags \
+		--negotiate-only \
+		--negotiation-tip=$(git -C client rev-parse HEAD) \
+		origin 2>err &&
+	test_i18ngrep "negotiate-only requires protocol v2" err
+'
+
 # DO NOT add non-httpd-specific tests here, because the last part of this
 # test script is only executed when httpd is available and enabled.
 
diff --git a/transport-helper.c b/transport-helper.c
index 4cd76366fa..4be035edb8 100644
--- a/transport-helper.c
+++ b/transport-helper.c
@@ -684,6 +684,16 @@ static int fetch(struct transport *transport,
 		return transport->vtable->fetch(transport, nr_heads, to_fetch);
 	}
 
+	/*
+	 * If we reach here, then the server, the client, and/or the transport
+	 * helper does not support protocol v2. --negotiate-only requires
+	 * protocol v2.
+	 */
+	if (data->transport_options.acked_commits) {
+		warning(_("--negotiate-only requires protocol v2"));
+		return -1;
+	}
+
 	if (!data->get_refs_list_called)
 		get_refs_list_using_list(transport, 0);
 
diff --git a/transport.c b/transport.c
index ef66e73090..80caeaa72f 100644
--- a/transport.c
+++ b/transport.c
@@ -392,16 +392,29 @@ static int fetch_refs_via_pack(struct transport *transport,
 	else if (data->version <= protocol_v1)
 		die_if_server_options(transport);
 
+	if (data->options.acked_commits) {
+		if (data->version < protocol_v2) {
+			warning(_("--negotiate-only requires protocol v2"));
+			ret = -1;
+		} else if (!server_supports_feature("fetch", "wait-for-done", 0)) {
+			warning(_("server does not support wait-for-done"));
+			ret = -1;
+		} else {
+			negotiate_using_fetch(data->options.negotiation_tips,
+					      transport->server_options,
+					      transport->stateless_rpc,
+					      data->fd,
+					      data->options.acked_commits);
+			ret = 0;
+		}
+		goto cleanup;
+	}
+
 	refs = fetch_pack(&args, data->fd,
 			  refs_tmp ? refs_tmp : transport->remote_refs,
 			  to_fetch, nr_heads, &data->shallow,
 			  &transport->pack_lockfiles, data->version);
 
-	close(data->fd[0]);
-	close(data->fd[1]);
-	if (finish_connect(data->conn))
-		ret = -1;
-	data->conn = NULL;
 	data->got_remote_heads = 0;
 	data->options.self_contained_and_connected =
 		args.self_contained_and_connected;
@@ -412,6 +425,13 @@ static int fetch_refs_via_pack(struct transport *transport,
 	if (report_unmatched_refs(to_fetch, nr_heads))
 		ret = -1;
 
+cleanup:
+	close(data->fd[0]);
+	close(data->fd[1]);
+	if (finish_connect(data->conn))
+		ret = -1;
+	data->conn = NULL;
+
 	free_refs(refs_tmp);
 	free_refs(refs);
 	return ret;
diff --git a/transport.h b/transport.h
index 4d5db0a7f2..1cbab11373 100644
--- a/transport.h
+++ b/transport.h
@@ -47,6 +47,12 @@ struct git_transport_options {
 	 * transport_set_option().
 	 */
 	struct oid_array *negotiation_tips;
+
+	/*
+	 * If allocated, whenever transport_fetch_refs() is called, add known
+	 * common commits to this oidset instead of fetching any packfiles.
+	 */
+	struct oidset *acked_commits;
 };
 
 enum transport_family {
diff --git a/upload-pack.c b/upload-pack.c
index e19583ae0f..b432ef0119 100644
--- a/upload-pack.c
+++ b/upload-pack.c
@@ -103,6 +103,7 @@ struct upload_pack_data {
 	unsigned use_ofs_delta : 1;
 	unsigned no_progress : 1;
 	unsigned use_include_tag : 1;
+	unsigned wait_for_done : 1;
 	unsigned allow_filter : 1;
 	unsigned allow_filter_fallback : 1;
 	unsigned long tree_filter_max_depth;
@@ -1496,6 +1497,10 @@ static void process_args(struct packet_reader *request,
 			data->done = 1;
 			continue;
 		}
+		if (!strcmp(arg, "wait-for-done")) {
+			data->wait_for_done = 1;
+			continue;
+		}
 
 		/* Shallow related arguments */
 		if (process_shallow(arg, &data->shallows))
@@ -1578,7 +1583,7 @@ static int send_acks(struct upload_pack_data *data, struct oid_array *acks)
 				    oid_to_hex(&acks->oid[i]));
 	}
 
-	if (ok_to_give_up(data)) {
+	if (!data->wait_for_done && ok_to_give_up(data)) {
 		/* Send Ready */
 		packet_writer_write(&data->writer, "ready\n");
 		return 1;
@@ -1668,10 +1673,13 @@ int upload_pack_v2(struct repository *r, struct strvec *keys,
 		case FETCH_PROCESS_ARGS:
 			process_args(request, &data);
 
-			if (!data.want_obj.nr) {
+			if (!data.want_obj.nr && !data.wait_for_done) {
 				/*
-				 * Request didn't contain any 'want' lines,
-				 * guess they didn't want anything.
+				 * Request didn't contain any 'want' lines (and
+				 * the request does not contain
+				 * "wait-for-done", in which it is reasonable
+				 * to just send 'have's without 'want's); guess
+				 * they didn't want anything.
 				 */
 				state = FETCH_DONE;
 			} else if (data.haves.nr) {
@@ -1723,7 +1731,7 @@ int upload_pack_advertise(struct repository *r,
 		int allow_sideband_all_value;
 		char *str = NULL;
 
-		strbuf_addstr(value, "shallow");
+		strbuf_addstr(value, "shallow wait-for-done");
 
 		if (!repo_config_get_bool(the_repository,
 					 "uploadpack.allowfilter",
-- 
2.31.1.527.g47e6f16901-goog


^ permalink raw reply	[flat|nested] 33+ messages in thread

* [PATCH v2 5/5] send-pack: support push negotiation
  2021-05-04 21:15 ` [PATCH v2 0/5] " Jonathan Tan
                     ` (3 preceding siblings ...)
  2021-05-04 21:16   ` [PATCH v2 4/5] fetch: teach independent negotiation (no packfile) Jonathan Tan
@ 2021-05-04 21:16   ` Jonathan Tan
  4 siblings, 0 replies; 33+ messages in thread
From: Jonathan Tan @ 2021-05-04 21:16 UTC (permalink / raw)
  To: git; +Cc: Jonathan Tan, gitster, stolee

Teach Git the push.negotiate config variable.

Signed-off-by: Jonathan Tan <jonathantanmy@google.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
---
 Documentation/config/push.txt |  7 ++++
 send-pack.c                   | 61 ++++++++++++++++++++++++++++++++---
 t/t5516-fetch-push.sh         | 35 ++++++++++++++++++++
 3 files changed, 99 insertions(+), 4 deletions(-)

diff --git a/Documentation/config/push.txt b/Documentation/config/push.txt
index 21b256e0a4..f2667b2689 100644
--- a/Documentation/config/push.txt
+++ b/Documentation/config/push.txt
@@ -120,3 +120,10 @@ push.useForceIfIncludes::
 	`--force-if-includes` as an option to linkgit:git-push[1]
 	in the command line. Adding `--no-force-if-includes` at the
 	time of push overrides this configuration setting.
+
+push.negotiate::
+	If set to "true", attempt to reduce the size of the packfile
+	sent by rounds of negotiation in which the client and the
+	server attempt to find commits in common. If "false", Git will
+	rely solely on the server's ref advertisement to find commits
+	in common.
diff --git a/send-pack.c b/send-pack.c
index 5f215b13c7..9cb9f71650 100644
--- a/send-pack.c
+++ b/send-pack.c
@@ -56,7 +56,9 @@ static void feed_object(const struct object_id *oid, FILE *fh, int negative)
 /*
  * Make a pack stream and spit it out into file descriptor fd
  */
-static int pack_objects(int fd, struct ref *refs, struct oid_array *extra, struct send_pack_args *args)
+static int pack_objects(int fd, struct ref *refs, struct oid_array *advertised,
+			struct oid_array *negotiated,
+			struct send_pack_args *args)
 {
 	/*
 	 * The child becomes pack-objects --revs; we feed
@@ -94,8 +96,10 @@ static int pack_objects(int fd, struct ref *refs, struct oid_array *extra, struc
 	 * parameters by writing to the pipe.
 	 */
 	po_in = xfdopen(po.in, "w");
-	for (i = 0; i < extra->nr; i++)
-		feed_object(&extra->oid[i], po_in, 1);
+	for (i = 0; i < advertised->nr; i++)
+		feed_object(&advertised->oid[i], po_in, 1);
+	for (i = 0; i < negotiated->nr; i++)
+		feed_object(&negotiated->oid[i], po_in, 1);
 
 	while (refs) {
 		if (!is_null_oid(&refs->old_oid))
@@ -409,11 +413,55 @@ static void reject_invalid_nonce(const char *nonce, int len)
 	}
 }
 
+static void get_commons_through_negotiation(const char *url,
+					    const struct ref *remote_refs,
+					    struct oid_array *commons)
+{
+	struct child_process child = CHILD_PROCESS_INIT;
+	const struct ref *ref;
+	int len = the_hash_algo->hexsz + 1; /* hash + NL */
+
+	child.git_cmd = 1;
+	child.no_stdin = 1;
+	child.out = -1;
+	strvec_pushl(&child.args, "fetch", "--negotiate-only", NULL);
+	for (ref = remote_refs; ref; ref = ref->next)
+		strvec_pushf(&child.args, "--negotiation-tip=%s", oid_to_hex(&ref->new_oid));
+	strvec_push(&child.args, url);
+
+	if (start_command(&child))
+		die(_("send-pack: unable to fork off fetch subprocess"));
+
+	do {
+		char hex_hash[GIT_MAX_HEXSZ + 1];
+		int read_len = read_in_full(child.out, hex_hash, len);
+		struct object_id oid;
+		const char *end;
+
+		if (!read_len)
+			break;
+		if (read_len != len)
+			die("invalid length read %d", read_len);
+		if (parse_oid_hex(hex_hash, &oid, &end) || *end != '\n')
+			die("invalid hash");
+		oid_array_append(commons, &oid);
+	} while (1);
+
+	if (finish_command(&child)) {
+		/*
+		 * The information that push negotiation provides is useful but
+		 * not mandatory.
+		 */
+		warning(_("push negotiation failed; proceeding anyway with push"));
+	}
+}
+
 int send_pack(struct send_pack_args *args,
 	      int fd[], struct child_process *conn,
 	      struct ref *remote_refs,
 	      struct oid_array *extra_have)
 {
+	struct oid_array commons = OID_ARRAY_INIT;
 	int in = fd[0];
 	int out = fd[1];
 	struct strbuf req_buf = STRBUF_INIT;
@@ -426,6 +474,7 @@ int send_pack(struct send_pack_args *args,
 	int quiet_supported = 0;
 	int agent_supported = 0;
 	int advertise_sid = 0;
+	int push_negotiate = 0;
 	int use_atomic = 0;
 	int atomic_supported = 0;
 	int use_push_options = 0;
@@ -437,6 +486,10 @@ int send_pack(struct send_pack_args *args,
 	const char *push_cert_nonce = NULL;
 	struct packet_reader reader;
 
+	git_config_get_bool("push.negotiate", &push_negotiate);
+	if (push_negotiate)
+		get_commons_through_negotiation(args->url, remote_refs, &commons);
+
 	git_config_get_bool("transfer.advertisesid", &advertise_sid);
 
 	/* Does the other end support the reporting? */
@@ -625,7 +678,7 @@ int send_pack(struct send_pack_args *args,
 			   PACKET_READ_DIE_ON_ERR_PACKET);
 
 	if (need_pack_data && cmds_sent) {
-		if (pack_objects(out, remote_refs, extra_have, args) < 0) {
+		if (pack_objects(out, remote_refs, extra_have, &commons, args) < 0) {
 			if (args->stateless_rpc)
 				close(out);
 			if (git_connection_is_socket(conn))
diff --git a/t/t5516-fetch-push.sh b/t/t5516-fetch-push.sh
index f11742ed59..0916f76302 100755
--- a/t/t5516-fetch-push.sh
+++ b/t/t5516-fetch-push.sh
@@ -191,6 +191,41 @@ test_expect_success 'fetch with pushInsteadOf (should not rewrite)' '
 	)
 '
 
+grep_wrote () {
+	object_count=$1
+	file_name=$2
+	grep 'write_pack_file/wrote.*"value":"'$1'"' $2
+}
+
+test_expect_success 'push with negotiation' '
+	# Without negotiation
+	mk_empty testrepo &&
+	git push testrepo $the_first_commit:refs/remotes/origin/first_commit &&
+	git -C testrepo config receive.hideRefs refs/remotes/origin/first_commit &&
+	echo now pushing without negotiation &&
+	GIT_TRACE2_EVENT="$(pwd)/event" git -c protocol.version=2 push testrepo refs/heads/main:refs/remotes/origin/main &&
+	grep_wrote 5 event && # 2 commits, 2 trees, 1 blob
+
+	# Same commands, but with negotiation
+	rm event &&
+	mk_empty testrepo &&
+	git push testrepo $the_first_commit:refs/remotes/origin/first_commit &&
+	git -C testrepo config receive.hideRefs refs/remotes/origin/first_commit &&
+	GIT_TRACE2_EVENT="$(pwd)/event" git -c protocol.version=2 -c push.negotiate=1 push testrepo refs/heads/main:refs/remotes/origin/main &&
+	grep_wrote 2 event # 1 commit, 1 tree
+'
+
+test_expect_success 'push with negotiation proceeds anyway even if negotiation fails' '
+	rm event &&
+	mk_empty testrepo &&
+	git push testrepo $the_first_commit:refs/remotes/origin/first_commit &&
+	git -C testrepo config receive.hideRefs refs/remotes/origin/first_commit &&
+	GIT_TEST_PROTOCOL_VERSION=0 GIT_TRACE2_EVENT="$(pwd)/event" \
+		git -c push.negotiate=1 push testrepo refs/heads/main:refs/remotes/origin/main 2>err &&
+	grep_wrote 5 event && # 2 commits, 2 trees, 1 blob
+	test_i18ngrep "push negotiation failed" err
+'
+
 test_expect_success 'push without wildcard' '
 	mk_empty testrepo &&
 
-- 
2.31.1.527.g47e6f16901-goog


^ permalink raw reply	[flat|nested] 33+ messages in thread

* Re: [PATCH v2 4/5] fetch: teach independent negotiation (no packfile)
  2021-05-04 21:16   ` [PATCH v2 4/5] fetch: teach independent negotiation (no packfile) Jonathan Tan
@ 2021-05-05  1:53     ` Junio C Hamano
  2021-05-05 16:42       ` Derrick Stolee
  2021-05-05 16:44     ` Derrick Stolee
  1 sibling, 1 reply; 33+ messages in thread
From: Junio C Hamano @ 2021-05-05  1:53 UTC (permalink / raw)
  To: Jonathan Tan; +Cc: git, stolee

Jonathan Tan <jonathantanmy@google.com> writes:

> +static int add_to_object_array(const struct object_id *oid, void *data)
> +{
> +	struct object_array *a = data;
> +
> +	add_object_array(lookup_object(the_repository, oid), "", a);

Moving to lookup_object() made me look around, but at this point the
object in question (which comes from the negotiation_tips) has been
instantiated, so it is OK.

    Side note. The big difference between lookup and parse is what
    happens when this process hasn't seen the object yet---the
    former will just return NULL instead of instantiating the
    in-core copy; for that reason, it is easier on the readers to
    use parse_object() if we know we want an in-core object *and*
    when we use it we want to see it parsed already).

> +static void clear_common_flag(struct oidset *s)
> +{
> +	struct oidset_iter iter;
> +	const struct object_id *oid;
> +	oidset_iter_init(s, &iter);
> +
> +	while ((oid = oidset_iter_next(&iter))) {
> +		struct object *obj = lookup_object(the_repository, oid);

This one obviously is OK ;-)  The fact we are clearing by definition
means we already do have in-core objects.

> +		obj->flags &= ~COMMON;
> +	}
> +}

Thanks.

^ permalink raw reply	[flat|nested] 33+ messages in thread

* Re: [PATCH v2 4/5] fetch: teach independent negotiation (no packfile)
  2021-05-05  1:53     ` Junio C Hamano
@ 2021-05-05 16:42       ` Derrick Stolee
  2021-05-06  2:12         ` Junio C Hamano
  0 siblings, 1 reply; 33+ messages in thread
From: Derrick Stolee @ 2021-05-05 16:42 UTC (permalink / raw)
  To: Junio C Hamano, Jonathan Tan; +Cc: git

On 5/4/2021 9:53 PM, Junio C Hamano wrote:
> Jonathan Tan <jonathantanmy@google.com> writes:
> 
>> +static int add_to_object_array(const struct object_id *oid, void *data)
>> +{
>> +	struct object_array *a = data;
>> +
>> +	add_object_array(lookup_object(the_repository, oid), "", a);
> 
> Moving to lookup_object() made me look around, but at this point the
> object in question (which comes from the negotiation_tips) has been
> instantiated, so it is OK.
> 
>     Side note. The big difference between lookup and parse is what
>     happens when this process hasn't seen the object yet---the
>     former will just return NULL instead of instantiating the
>     in-core copy; for that reason, it is easier on the readers to
>     use parse_object() if we know we want an in-core object *and*
>     when we use it we want to see it parsed already).

Please forgive my incorrect recommendation here. I was expecting
lookup_object() to behave like lookup_commit(), which creates the
object if it is not already in the cached set.

>> +static void clear_common_flag(struct oidset *s)
>> +{
>> +	struct oidset_iter iter;
>> +	const struct object_id *oid;
>> +	oidset_iter_init(s, &iter);
>> +
>> +	while ((oid = oidset_iter_next(&iter))) {
>> +		struct object *obj = lookup_object(the_repository, oid);
> 
> This one obviously is OK ;-)  The fact we are clearing by definition
> means we already do have in-core objects.

Thanks for your careful eye here.

-Stolee

^ permalink raw reply	[flat|nested] 33+ messages in thread

* Re: [PATCH v2 4/5] fetch: teach independent negotiation (no packfile)
  2021-05-04 21:16   ` [PATCH v2 4/5] fetch: teach independent negotiation (no packfile) Jonathan Tan
  2021-05-05  1:53     ` Junio C Hamano
@ 2021-05-05 16:44     ` Derrick Stolee
  1 sibling, 0 replies; 33+ messages in thread
From: Derrick Stolee @ 2021-05-05 16:44 UTC (permalink / raw)
  To: Jonathan Tan, git; +Cc: gitster

On 5/4/2021 5:16 PM, Jonathan Tan wrote:

> +void negotiate_using_fetch(const struct oid_array *negotiation_tips,
> +			   const struct string_list *server_options,
> +			   int stateless_rpc,
> +			   int fd[],
> +			   struct oidset *acked_commits)
> +{
> +	struct fetch_negotiator negotiator;
> +	struct packet_reader reader;
> +	struct object_array nt_object_array = OBJECT_ARRAY_INIT;
> +	struct strbuf req_buf = STRBUF_INIT;
> +	int haves_to_send = INITIAL_FLUSH;
> +	int in_vain = 0;
> +	int seen_ack = 0;
> +	int last_iteration = 0;
> +	timestamp_t min_generation = GENERATION_NUMBER_INFINITY;

...

> +		/* Process ACKs/NAKs */
> +		process_section_header(&reader, "acknowledgments", 0);
> +		while (process_ack(&negotiator, &reader, &common_oid,
> +				   &received_ready)) {
> +			struct commit *commit = lookup_commit(the_repository,
> +							      &common_oid);
> +			if (commit) {
> +				timestamp_t generation;
> +
> +				parse_commit_or_die(commit);
> +				commit->object.flags |= COMMON;
> +				generation = commit_graph_generation(commit);
> +				if (generation < min_generation)
> +					min_generation = generation;
> +			}
> +			in_vain = 0;
> +			seen_ack = 1;
> +			oidset_insert(acked_commits, &common_oid);
> +		}
> +		if (received_ready)
> +			die(_("unexpected 'ready' from remote"));
> +		else
> +			do_check_stateless_delimiter(stateless_rpc, &reader);
> +		if (can_all_from_reach_with_flag(&nt_object_array, COMMON,
> +						 REACH_SCRATCH, 0,
> +						 min_generation))
> +			last_iteration = 1;

I'm just chiming in to confirm that this use of min_generation is
correct. Thanks!

-Stolee

^ permalink raw reply	[flat|nested] 33+ messages in thread

* Re: [PATCH v2 4/5] fetch: teach independent negotiation (no packfile)
  2021-05-05 16:42       ` Derrick Stolee
@ 2021-05-06  2:12         ` Junio C Hamano
  0 siblings, 0 replies; 33+ messages in thread
From: Junio C Hamano @ 2021-05-06  2:12 UTC (permalink / raw)
  To: Derrick Stolee; +Cc: Jonathan Tan, git

Derrick Stolee <stolee@gmail.com> writes:

>> Moving to lookup_object() made me look around, but at this point the
>> object in question (which comes from the negotiation_tips) has been
>> instantiated, so it is OK.
>> 
>>     Side note. The big difference between lookup and parse is what
>>     happens when this process hasn't seen the object yet---the
>>     former will just return NULL instead of instantiating the
>>     in-core copy; for that reason, it is easier on the readers to
>>     use parse_object() if we know we want an in-core object *and*
>>     when we use it we want to see it parsed already).
>
> Please forgive my incorrect recommendation here. I was expecting
> lookup_object() to behave like lookup_commit(), which creates the
> object if it is not already in the cached set.

It is not wrong per-se to recommend or use lookup_object() in this
case, as long as who recommends or uses the function is certain that
the object should already exist in-core.

But it is just that the lookup_object() is often not what the caller
wants to use; it is a very rare use case for a caller to be able to
say "I am OK for you to return NULL to me for this object, even if
it is in our object store, when we do not yet have it in-core".  The
only exception is the implementation of lookup_<type>() helpers,
where they handle "not loaded yet" answer from lookup_object() with
create_object() and always return usable in-core object to the
caller.

So the sole practical use case for lookup_object() outside the
lookup_<type>() implementation becomes "I am 100% sure that an
object with this object name has already been loaded in-core, so
please let me access it", which may be optimized for a wrong case
(because most of the API pass in-core objects, not object names,
around).  I am not sure if this particular API strangeness can be
remedied, though.

Thanks.

^ permalink raw reply	[flat|nested] 33+ messages in thread

end of thread, other threads:[~2021-05-06  2:12 UTC | newest]

Thread overview: 33+ messages (download: mbox.gz / follow: Atom feed)
-- links below jump to the message on this page --
2021-04-09  1:09 [PATCH 0/6] Push negotiation Jonathan Tan
2021-04-09  1:09 ` [PATCH 1/6] fetch-pack: buffer object-format with other args Jonathan Tan
2021-04-09  4:49   ` Junio C Hamano
2021-04-09 16:24     ` Jonathan Tan
2021-04-09  1:09 ` [PATCH 2/6] fetch-pack: refactor process_acks() Jonathan Tan
2021-04-09  5:08   ` Junio C Hamano
2021-05-03 16:30   ` Derrick Stolee
2021-04-09  1:10 ` [PATCH 3/6] fetch-pack: refactor add_haves() Jonathan Tan
2021-04-09  5:20   ` Junio C Hamano
2021-04-09  1:10 ` [PATCH 4/6] fetch-pack: refactor command and capability write Jonathan Tan
2021-04-09  5:27   ` Junio C Hamano
2021-04-09  1:10 ` [PATCH 5/6] fetch: teach independent negotiation (no packfile) Jonathan Tan
2021-04-09  5:41   ` Junio C Hamano
2021-04-09 16:38     ` Jonathan Tan
2021-05-03 15:25   ` Derrick Stolee
2021-05-03 15:40     ` Derrick Stolee
2021-05-03 21:52     ` Jonathan Tan
2021-04-09  1:10 ` [PATCH 6/6] send-pack: support push negotiation Jonathan Tan
2021-05-03 15:35   ` Derrick Stolee
2021-05-03 22:02     ` Jonathan Tan
2021-05-04 17:26       ` Derrick Stolee
2021-04-30  5:42 ` [PATCH 0/6] Push negotiation Junio C Hamano
2021-04-30 17:33   ` Derrick Stolee
2021-05-04 21:15 ` [PATCH v2 0/5] " Jonathan Tan
2021-05-04 21:15   ` [PATCH v2 1/5] fetch-pack: refactor process_acks() Jonathan Tan
2021-05-04 21:15   ` [PATCH v2 2/5] fetch-pack: refactor add_haves() Jonathan Tan
2021-05-04 21:16   ` [PATCH v2 3/5] fetch-pack: refactor command and capability write Jonathan Tan
2021-05-04 21:16   ` [PATCH v2 4/5] fetch: teach independent negotiation (no packfile) Jonathan Tan
2021-05-05  1:53     ` Junio C Hamano
2021-05-05 16:42       ` Derrick Stolee
2021-05-06  2:12         ` Junio C Hamano
2021-05-05 16:44     ` Derrick Stolee
2021-05-04 21:16   ` [PATCH v2 5/5] send-pack: support push negotiation Jonathan Tan

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