[PATCH 0/2] Skip ls-refs if possible for HTTP

[PATCH 0/2] Skip ls-refs if possible for HTTP

[Jonathan Tan]

This was discovered by one of my colleagues when using a partial clone.
I thought I had resolved the problem with the commits mentioned in patch
1 (e70a3030e7 and ancestors), but apparently that is not the case (that
only worked for native protocols). So here is a fix for HTTP.

I'm not sure of the value of the test in patch 2, but that test does
fail if I don't update fetch_refs_from_bundle() to first call
get_refs_from_bundle() if it hasn't already been called.

Jonathan Tan (2):
  transport-helper: skip ls-refs if unnecessary
  transport: teach all vtables to allow fetch first

 t/t5607-clone-bundle.sh | 11 +++++++++++
 t/t5702-protocol-v2.sh  | 13 +++++++++++++
 transport-helper.c      | 38 ++++++++++++++++++++++++++++++++------
 transport-internal.h    |  6 ------
 transport.c             | 18 ++++++------------
 5 files changed, 62 insertions(+), 24 deletions(-)

-- 
2.23.0.187.g17f5b7556c-goog

[PATCH 1/2] transport-helper: skip ls-refs if unnecessary

[Jonathan Tan]

Commit e70a3030e7 ("fetch: do not list refs if fetching only hashes",
2018-10-07) and its ancestors taught Git, as an optimization, to skip
the ls-refs step when it is not necessary during a protocol v2 fetch
(for example, when lazy fetching a missing object in a partial clone, or
when running "git fetch --no-tags <remote> <SHA-1>"). But that was only
done for natively supported protocols; in particular, HTTP was not
supported.

Teach Git to skip ls-refs when using remote helpers that support connect
or stateless-connect. To do this, fetch() is made an acceptable entry
point. Because fetch() can now be the first function in the vtable
called, "get_helper(transport);" has to be added to the beginning of
that function to set the transport up (if not yet set up) before
process_connect() is invoked.

When fetch() is called, the transport could be taken over (this happens
if "connect" or "stateless-connect" is successfully run without any
"fallback" response), or not. If the transport is taken over, execution
continues like execution for natively supported protocols
(fetch_refs_via_pack() is executed, which will fetch refs using ls-refs
if needed). If not, the remote helper interface will invoke
get_refs_list() if it hasn't been invoked yet, preserving existing
behavior.

Signed-off-by: Jonathan Tan <jonathantanmy@google.com>
---
 t/t5702-protocol-v2.sh | 13 +++++++++++++
 transport-helper.c     | 39 +++++++++++++++++++++++++++++++++------
 2 files changed, 46 insertions(+), 6 deletions(-)

diff --git a/t/t5702-protocol-v2.sh b/t/t5702-protocol-v2.sh
index 011b81d4fc..61f5080de0 100755
--- a/t/t5702-protocol-v2.sh
+++ b/t/t5702-protocol-v2.sh
@@ -631,6 +631,19 @@ test_expect_success 'fetch with http:// using protocol v2' '
 	grep "git< version 2" log
 '
 
+test_expect_success 'fetch with http:// by hash without tag following with protocol v2 does not list refs' '
+	test_when_finished "rm -f log" &&
+
+	test_commit -C "$HTTPD_DOCUMENT_ROOT_PATH/http_parent" two_a &&
+	git -C "$HTTPD_DOCUMENT_ROOT_PATH/http_parent" rev-parse two_a >two_a_hash &&
+
+	GIT_TRACE_PACKET="$(pwd)/log" git -C http_child -c protocol.version=2 \
+		fetch --no-tags origin $(cat two_a_hash) &&
+
+	grep "fetch< version 2" log &&
+	! grep "fetch> command=ls-refs" log
+'
+
 test_expect_success 'fetch from namespaced repo respects namespaces' '
 	test_when_finished "rm -f log" &&
 
diff --git a/transport-helper.c b/transport-helper.c
index 6b05a88faf..1fb31e1a6e 100644
--- a/transport-helper.c
+++ b/transport-helper.c
@@ -33,6 +33,16 @@ struct helper_data {
 		check_connectivity : 1,
 		no_disconnect_req : 1,
 		no_private_update : 1;
+
+	/*
+	 * As an optimization, the transport code may invoke fetch before
+	 * get_refs_list. If this happens, and if the transport helper doesn't
+	 * support connect or stateless_connect, we need to invoke
+	 * get_refs_list ourselves if we haven't already done so. Keep track of
+	 * whether we have invoked get_refs_list.
+	 */
+	unsigned get_refs_list_called : 1;
+
 	char *export_marks;
 	char *import_marks;
 	/* These go from remote name (as in "list") to private name */
@@ -652,17 +662,25 @@ static int connect_helper(struct transport *transport, const char *name,
 	return 0;
 }
 
+static struct ref *get_refs_list_using_list(struct transport *transport,
+					    int for_push);
+
 static int fetch(struct transport *transport,
 		 int nr_heads, struct ref **to_fetch)
 {
 	struct helper_data *data = transport->data;
 	int i, count;
 
+	get_helper(transport);
+
 	if (process_connect(transport, 0)) {
 		do_take_over(transport);
 		return transport->vtable->fetch(transport, nr_heads, to_fetch);
 	}
 
+	if (!data->get_refs_list_called)
+		get_refs_list_using_list(transport, 0);
+
 	count = 0;
 	for (i = 0; i < nr_heads; i++)
 		if (!(to_fetch[i]->status & REF_STATUS_UPTODATE))
@@ -1058,6 +1076,19 @@ static int has_attribute(const char *attrs, const char *attr)
 
 static struct ref *get_refs_list(struct transport *transport, int for_push,
 				 const struct argv_array *ref_prefixes)
+{
+	get_helper(transport);
+
+	if (process_connect(transport, for_push)) {
+		do_take_over(transport);
+		return transport->vtable->get_refs_list(transport, for_push, ref_prefixes);
+	}
+
+	return get_refs_list_using_list(transport, for_push);
+}
+
+static struct ref *get_refs_list_using_list(struct transport *transport,
+					    int for_push)
 {
 	struct helper_data *data = transport->data;
 	struct child_process *helper;
@@ -1066,13 +1097,9 @@ static struct ref *get_refs_list(struct transport *transport, int for_push,
 	struct ref *posn;
 	struct strbuf buf = STRBUF_INIT;
 
+	data->get_refs_list_called = 1;
 	helper = get_helper(transport);
 
-	if (process_connect(transport, for_push)) {
-		do_take_over(transport);
-		return transport->vtable->get_refs_list(transport, for_push, ref_prefixes);
-	}
-
 	if (data->push && for_push)
 		write_str_in_full(helper->in, "list for-push\n");
 	else
@@ -1119,7 +1146,7 @@ static struct ref *get_refs_list(struct transport *transport, int for_push,
 }
 
 static struct transport_vtable vtable = {
-	0,
+	1,
 	set_helper_option,
 	get_refs_list,
 	fetch,
-- 
2.23.0.187.g17f5b7556c-goog

[PATCH 2/2] transport: teach all vtables to allow fetch first

[Jonathan Tan]

The only transport that does not allow fetch() to be called before
get_refs_list() is the bundle transport. Clean up the code by teaching
the bundle transport the ability to do this, and removing support for
transports that don't support this order of invocation.

Signed-off-by: Jonathan Tan <jonathantanmy@google.com>
---
 t/t5607-clone-bundle.sh | 11 +++++++++++
 transport-helper.c      |  1 -
 transport-internal.h    |  6 ------
 transport.c             | 18 ++++++------------
 4 files changed, 17 insertions(+), 19 deletions(-)

diff --git a/t/t5607-clone-bundle.sh b/t/t5607-clone-bundle.sh
index 2a0fb15cf1..b7a3fdf02d 100755
--- a/t/t5607-clone-bundle.sh
+++ b/t/t5607-clone-bundle.sh
@@ -83,4 +83,15 @@ test_expect_success 'failed bundle creation does not leave cruft' '
 	test_path_is_missing fail.bundle.lock
 '
 
+test_expect_success 'fetch SHA-1 from bundle' '
+	test_create_repo foo &&
+	test_commit -C foo x &&
+	git -C foo bundle create tip.bundle -1 master &&
+	git -C foo rev-parse HEAD >hash &&
+
+	# Exercise to ensure that fetching a SHA-1 from a bundle works with no
+	# errors
+	git fetch --no-tags foo/tip.bundle "$(cat hash)"
+'
+
 test_done
diff --git a/transport-helper.c b/transport-helper.c
index 1fb31e1a6e..96955d4004 100644
--- a/transport-helper.c
+++ b/transport-helper.c
@@ -1146,7 +1146,6 @@ static struct ref *get_refs_list_using_list(struct transport *transport,
 }
 
 static struct transport_vtable vtable = {
-	1,
 	set_helper_option,
 	get_refs_list,
 	fetch,
diff --git a/transport-internal.h b/transport-internal.h
index 004bee5e36..1cde6258a7 100644
--- a/transport-internal.h
+++ b/transport-internal.h
@@ -6,12 +6,6 @@ struct transport;
 struct argv_array;
 
 struct transport_vtable {
-	/**
-	 * This transport supports the fetch() function being called
-	 * without get_refs_list() first being called.
-	 */
-	unsigned fetch_without_list : 1;
-
 	/**
 	 * Returns 0 if successful, positive if the option is not
 	 * recognized or is inapplicable, and negative if the option
diff --git a/transport.c b/transport.c
index 778c60bf57..662a2d9ae0 100644
--- a/transport.c
+++ b/transport.c
@@ -122,6 +122,7 @@ static void set_upstreams(struct transport *transport, struct ref *refs,
 struct bundle_transport_data {
 	int fd;
 	struct bundle_header header;
+	unsigned get_refs_from_bundle_called : 1;
 };
 
 static struct ref *get_refs_from_bundle(struct transport *transport,
@@ -135,6 +136,8 @@ static struct ref *get_refs_from_bundle(struct transport *transport,
 	if (for_push)
 		return NULL;
 
+	data->get_refs_from_bundle_called = 1;
+
 	if (data->fd > 0)
 		close(data->fd);
 	data->fd = read_bundle_header(transport->url, &data->header);
@@ -154,6 +157,9 @@ static int fetch_refs_from_bundle(struct transport *transport,
 			       int nr_heads, struct ref **to_fetch)
 {
 	struct bundle_transport_data *data = transport->data;
+
+	if (!data->get_refs_from_bundle_called)
+		get_refs_from_bundle(transport, 0, NULL);
 	return unbundle(the_repository, &data->header, data->fd,
 			transport->progress ? BUNDLE_VERBOSE : 0);
 }
@@ -742,7 +748,6 @@ static int disconnect_git(struct transport *transport)
 }
 
 static struct transport_vtable taken_over_vtable = {
-	1,
 	NULL,
 	get_refs_via_connect,
 	fetch_refs_via_pack,
@@ -892,7 +897,6 @@ void transport_check_allowed(const char *type)
 }
 
 static struct transport_vtable bundle_vtable = {
-	0,
 	NULL,
 	get_refs_from_bundle,
 	fetch_refs_from_bundle,
@@ -902,7 +906,6 @@ static struct transport_vtable bundle_vtable = {
 };
 
 static struct transport_vtable builtin_smart_vtable = {
-	1,
 	NULL,
 	get_refs_via_connect,
 	fetch_refs_via_pack,
@@ -1285,15 +1288,6 @@ int transport_fetch_refs(struct transport *transport, struct ref *refs)
 	struct ref **heads = NULL;
 	struct ref *rm;
 
-	if (!transport->vtable->fetch_without_list)
-		/*
-		 * Some transports (e.g. the built-in bundle transport and the
-		 * transport helper interface) do not work when fetching is
-		 * done immediately after transport creation. List the remote
-		 * refs anyway (if not already listed) as a workaround.
-		 */
-		transport_get_remote_refs(transport, NULL);
-
 	for (rm = refs; rm; rm = rm->next) {
 		nr_refs++;
 		if (rm->peer_ref &&
-- 
2.23.0.187.g17f5b7556c-goog

Re: [PATCH 0/2] Skip ls-refs if possible for HTTP

[Junio C Hamano]

Jonathan Tan <jonathantanmy@google.com> writes:

> This was discovered by one of my colleagues when using a partial clone.
> I thought I had resolved the problem with the commits mentioned in patch
> 1 (e70a3030e7 and ancestors), but apparently that is not the case (that
> only worked for native protocols). So here is a fix for HTTP.
>
> I'm not sure of the value of the test in patch 2, but that test does
> fail if I don't update fetch_refs_from_bundle() to first call
> get_refs_from_bundle() if it hasn't already been called.

This probably is totally off-tangent, but do any of these "let's
advertise fewer" changes at the protocol level have to take into
account the use of --prune option on the client side?

> Jonathan Tan (2):
>   transport-helper: skip ls-refs if unnecessary
>   transport: teach all vtables to allow fetch first
>
>  t/t5607-clone-bundle.sh | 11 +++++++++++
>  t/t5702-protocol-v2.sh  | 13 +++++++++++++
>  transport-helper.c      | 38 ++++++++++++++++++++++++++++++++------
>  transport-internal.h    |  6 ------
>  transport.c             | 18 ++++++------------
>  5 files changed, 62 insertions(+), 24 deletions(-)

Re: [PATCH 0/2] Skip ls-refs if possible for HTTP

[Jonathan Tan]

> This probably is totally off-tangent, but do any of these "let's
> advertise fewer" changes at the protocol level have to take into
> account the use of --prune option on the client side?

I don't think so. According to what I understand from the documentation,
the prune option prunes based on the RHS of the refspec, and it doesn't
affect anything non-matching. When we advertise fewer, the only refs
that are missing are those that are non-matching anyway.

Some experimentation seems to show that that is the case also:

$ git init one
[snip]
$ git -C one commit --allow-empty -m x
[master (root-commit) 67056ac] x
$ git -C one branch maste
$ git -C one branch other
$ git clone "$(pwd)/one" two
Cloning into 'two'...
done.
$ git -C one branch -d maste
Deleted branch maste (was 67056ac).
$ git -C two checkout --detach HEAD
HEAD is now at 67056ac x
$ GIT_TRACE_PACKET=1 git -c protocol.version=2 -C two fetch --prune origin refs/heads/m*:refs/remotes/origin/m*
[snipped lots of stuff; basically, only refs/heads/master is sent]
10:15:46.308264 pkt-line.c:80           packet:        fetch> ref-prefix refs/heads/m
10:15:46.308276 pkt-line.c:80           packet:        fetch> ref-prefix refs/tags/
10:15:46.308523 pkt-line.c:80           packet:        fetch< 67056ac6d07814334716df760054ac5bec05b66a refs/heads/master
From /usr/local/google/home/jonathantanmy/tmp/g/one
 - [deleted]         (none)     -> origin/maste
$ git -C two for-each-ref
67056ac6d07814334716df760054ac5bec05b66a commit	refs/heads/master
67056ac6d07814334716df760054ac5bec05b66a commit	refs/remotes/origin/HEAD
67056ac6d07814334716df760054ac5bec05b66a commit	refs/remotes/origin/master
67056ac6d07814334716df760054ac5bec05b66a commit	refs/remotes/origin/other

(Notice that refs/remotes/origin/other is untouched.)