[PATCH 5/7] push --lockref: implement logic to populate old_sha1_expect[]

[Junio C Hamano <gitster@pobox.com>]

This plugs the push_cas_option data collected by the command line
option parser to the transport system with a new function
apply_push_cas(), which is called after match_push_refs() has
already been called.  At this point, we know which remote we are
talking to, and what remote refs we are going to update, so we can
fill in the details that may have been missing from the command
line, such as

 (1) what abbreviated refname the user gave us matches the actual
     refname at the remote; and

 (2) which remote tracking branch in our local repository to read the
     value of the object to expect at the remote.

to populate the old_sha1_expect[] field of each of the remote ref.

Signed-off-by: Junio C Hamano <gitster@pobox.com>
---
 builtin/push.c      |  6 ++++++
 builtin/send-pack.c |  3 +++
 remote.c            | 61 +++++++++++++++++++++++++++++++++++++++++++++++++++++
 remote.h            |  3 +++
 transport.c         |  6 ++++++
 transport.h         |  4 ++++
 6 files changed, 83 insertions(+)

diff --git a/builtin/push.c b/builtin/push.c
index 31a5ba0..b0e3691 100644
--- a/builtin/push.c
+++ b/builtin/push.c
@@ -299,6 +299,12 @@ static int push_with_options(struct transport *transport, int flags)
 	if (thin)
 		transport_set_option(transport, TRANS_OPT_THIN, "yes");
 
+	if (!is_empty_cas(&cas)) {
+		if (!transport->smart_options)
+			die("underlying transport does not support --lockref option");
+		transport->smart_options->cas = &cas;
+	}
+
 	if (verbosity > 0)
 		fprintf(stderr, _("Pushing to %s\n"), transport->url);
 	err = transport_push(transport, refspec_nr, refspec, flags,
diff --git a/builtin/send-pack.c b/builtin/send-pack.c
index 061e2b2..41dc512 100644
--- a/builtin/send-pack.c
+++ b/builtin/send-pack.c
@@ -247,6 +247,9 @@ int cmd_send_pack(int argc, const char **argv, const char *prefix)
 	if (match_push_refs(local_refs, &remote_refs, nr_refspecs, refspecs, flags))
 		return -1;
 
+	if (!is_empty_cas(&cas))
+		apply_push_cas(&cas, remote, remote_refs);
+
 	set_ref_status_for_push(remote_refs, args.send_mirror,
 		args.force_update);
 
diff --git a/remote.c b/remote.c
index e9b423a..db418ff 100644
--- a/remote.c
+++ b/remote.c
@@ -1997,3 +1997,64 @@ int parse_push_cas_option(struct push_cas_option *cas, const char *arg, int unse
 		return error("cannot parse expected object name '%s'", colon + 1);
 	return 0;
 }
+
+int is_empty_cas(const struct push_cas_option *cas)
+{
+	return !cas->use_tracking_for_rest && !cas->nr;
+}
+
+/*
+ * Look at remote.fetch refspec and see if we have a remote
+ * tracking branch for the refname there.  Fill its current
+ * value in sha1[].
+ * If we cannot do so, return negative to signal an error.
+ */
+static int remote_tracking(struct remote *remote, const char *refname,
+			   unsigned char sha1[20])
+{
+	char *dst;
+
+	dst = apply_refspecs(remote->fetch, remote->fetch_refspec_nr, refname);
+	if (!dst)
+		return -1; /* no tracking ref for refname at remote */
+	if (read_ref(dst, sha1))
+		return -1; /* we know what the tracking ref is but we cannot read it */
+	return 0;
+}
+
+static void apply_cas(struct push_cas_option *cas,
+		      struct remote *remote,
+		      struct ref *ref)
+{
+	int i;
+
+	/* Find an explicit --lockref=<name>[:<value>] entry */
+	for (i = 0; i < cas->nr; i++) {
+		struct push_cas *entry = &cas->entry[i];
+		if (!refname_match(entry->refname, ref->name, ref_rev_parse_rules))
+			continue;
+		ref->expect_old_sha1 = 1;
+		if (!entry->use_tracking)
+			hashcpy(ref->old_sha1_expect, cas->entry[i].expect);
+		else if (remote_tracking(remote, ref->name, ref->old_sha1_expect))
+			ref->expect_old_no_trackback = 1;
+		return;
+	}
+
+	/* Are we using "--lockref" to cover all? */
+	if (!cas->use_tracking_for_rest)
+		return;
+
+	ref->expect_old_sha1 = 1;
+	if (remote_tracking(remote, ref->name, ref->old_sha1_expect))
+		ref->expect_old_no_trackback = 1;
+}
+
+void apply_push_cas(struct push_cas_option *cas,
+		    struct remote *remote,
+		    struct ref *remote_refs)
+{
+	struct ref *ref;
+	for (ref = remote_refs; ref; ref = ref->next)
+		apply_cas(cas, remote, ref);
+}
diff --git a/remote.h b/remote.h
index 28eb6a3..baa1c68 100644
--- a/remote.h
+++ b/remote.h
@@ -252,4 +252,7 @@ extern int parseopt_push_cas_option(const struct option *, const char *arg, int
 extern int parse_push_cas_option(struct push_cas_option *, const char *arg, int unset);
 extern void clear_cas_option(struct push_cas_option *);
 
+extern int is_empty_cas(const struct push_cas_option *);
+void apply_push_cas(struct push_cas_option *, struct remote *, struct ref *);
+
 #endif
diff --git a/transport.c b/transport.c
index 98f5270..b321d6a 100644
--- a/transport.c
+++ b/transport.c
@@ -1147,6 +1147,12 @@ int transport_push(struct transport *transport,
 			return -1;
 		}
 
+		if (transport->smart_options &&
+		    transport->smart_options->cas &&
+		    !is_empty_cas(transport->smart_options->cas))
+			apply_push_cas(transport->smart_options->cas,
+				       transport->remote, remote_refs);
+
 		set_ref_status_for_push(remote_refs,
 			flags & TRANSPORT_PUSH_MIRROR,
 			flags & TRANSPORT_PUSH_FORCE);
diff --git a/transport.h b/transport.h
index b551f99..10f7556 100644
--- a/transport.h
+++ b/transport.h
@@ -14,6 +14,7 @@ struct git_transport_options {
 	int depth;
 	const char *uploadpack;
 	const char *receivepack;
+	struct push_cas_option *cas;
 };
 
 struct transport {
@@ -127,6 +128,9 @@ struct transport *transport_get(struct remote *, const char *);
 /* Transfer the data as a thin pack if not null */
 #define TRANS_OPT_THIN "thin"
 
+/* Check the current value of the remote ref */
+#define TRANS_OPT_CAS "cas"
+
 /* Keep the pack that was transferred if not null */
 #define TRANS_OPT_KEEP "keep"
 
-- 
1.8.3.2-875-g76c723c