[PATCH 19/21] remote: make guess_remote_head() use exact HEAD lookup if it is available

[Jay Soffian <jaysoffian@gmail.com>]

From: Jeff King <peff@peff.net>

Our usual method for determining the ref pointed to by HEAD
is to compare HEAD's sha1 to the sha1 of all refs, trying to
find a unique match.

However, some transports actually get to look at HEAD
directly; we should make use of that information when it is
available.  Currently, only http remotes support this
feature.

Signed-off-by: Jeff King <peff@peff.net>
Signed-off-by: Jay Soffian <jaysoffian@gmail.com>
---
 remote.c              |   10 ++++++++++
 t/t5550-http-fetch.sh |   11 +++++++++++
 2 files changed, 21 insertions(+), 0 deletions(-)

diff --git a/remote.c b/remote.c
index 926f842..1c09cf0 100644
--- a/remote.c
+++ b/remote.c
@@ -1475,6 +1475,16 @@ struct ref *guess_remote_head(const struct ref *head,
 	if (!head)
 		return NULL;
 
+	/*
+	 * Some transports support directly peeking at
+	 * where HEAD points; if that is the case, then
+	 * we don't have to guess.
+	 */
+	if (head->symref) {
+		r = find_ref_by_name(refs, head->symref);
+		return r ? copy_ref_with_peer(r) : NULL;
+	}
+
 	/* If refs/heads/master could be right, it is. */
 	if (!all) {
 		r = find_ref_by_name(refs, "refs/heads/master");
diff --git a/t/t5550-http-fetch.sh b/t/t5550-http-fetch.sh
index b6e6ec9..05b1b62 100755
--- a/t/t5550-http-fetch.sh
+++ b/t/t5550-http-fetch.sh
@@ -42,5 +42,16 @@ test_expect_success 'fetch changes via http' '
 	test_cmp file clone/file
 '
 
+test_expect_success 'http remote detects correct HEAD' '
+	git push public master:other &&
+	(cd clone &&
+	 git remote set-head origin -d &&
+	 git remote set-head origin -a &&
+	 git symbolic-ref refs/remotes/origin/HEAD > output &&
+	 echo refs/remotes/origin/master > expect &&
+	 test_cmp expect output
+	)
+'
+
 stop_httpd
 test_done
-- 
1.6.2.rc1.291.g83eb