remote: make guess_remote_head() use exact HEAD lookup if it is available

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>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

diff --git a/remote.c b/remote.c
index 2123005d4bade5688ad03c97edecd6f84a157e17..9b8522db35367e5a698bebfcac9c3a107bfa5298 100644 (file)
--- a/remote.c
+++ b/remote.c
@@ -1476,6 +1476,14 @@ 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)
+               return copy_ref(find_ref_by_name(refs, head->symref));
+
        /* 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 b6e6ec96075d8e8485de466c4c5c6f325e7b0d62..05b1b62cb66956bca57e1fbacac534993637bdd9 100755 (executable)
--- 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