[PATCH 4/5] remote.c: teach branch_get() to treat symrefs other than HEAD

[Ramkumar Ramachandra <artagnon@gmail.com>]

Currently, branch_get() either accepts either a branch name, empty
string, or the magic four-letter word "HEAD".  Make it additionally
handle symbolic refs that point to a branch.

Update sha1_name.c:interpret_branch_name() to look for "@{", not '@'
(since '@' is a valid symbolic ref).

These two changes together make the failing test in t1508
(at-combinations) pass.  In other words, you can now do:

    $ git symbolic-ref @ HEAD

And expect the following to work:

    $ git rev-parse @@{u}

Signed-off-by: Ramkumar Ramachandra <artagnon@gmail.com>
---
 remote.c                   | 14 ++++++++++++++
 sha1_name.c                |  2 +-
 t/t1508-at-combinations.sh |  2 +-
 3 files changed, 16 insertions(+), 2 deletions(-)

diff --git a/remote.c b/remote.c
index 68eb99b..0f44e2e 100644
--- a/remote.c
+++ b/remote.c
@@ -1470,6 +1470,20 @@ struct branch *branch_get(const char *name)
 		ret = current_branch;
 	else
 		ret = make_branch(name, 0);
+
+	if (name && *name && (!ret || !ret->remote_name)) {
+		/* Is this a symref pointing to a valid branch, other
+		 * than HEAD?
+		 */
+		const char *this_ref;
+		unsigned char sha1[20];
+		int flag;
+
+		this_ref = resolve_ref_unsafe(name, sha1, 0, &flag);
+		if (this_ref && (flag & REF_ISSYMREF) &&
+			!prefixcmp(this_ref, "refs/heads/"))
+			ret = make_branch(this_ref + strlen("refs/heads/"), 0);
+	}
 	if (ret && ret->remote_name) {
 		ret->remote = remote_get(ret->remote_name);
 		if (ret->merge_nr) {
diff --git a/sha1_name.c b/sha1_name.c
index f30e344..c4a3a54 100644
--- a/sha1_name.c
+++ b/sha1_name.c
@@ -1060,7 +1060,7 @@ int interpret_branch_name(const char *name, struct strbuf *buf)
 		return ret - used + len;
 	}
 
-	cp = strchr(name, '@');
+	cp = strstr(name, "@{");
 	if (!cp)
 		return -1;
 	tmp_len = upstream_mark(cp, namelen - (cp - name));
diff --git a/t/t1508-at-combinations.sh b/t/t1508-at-combinations.sh
index efa2a2a..73c457d 100755
--- a/t/t1508-at-combinations.sh
+++ b/t/t1508-at-combinations.sh
@@ -59,7 +59,7 @@ nonsense "HEAD@{-1}"
 git symbolic-ref @ HEAD
 check "@@{1}" new-one
 check "@@{now}" new-two
-check "@@{u}" upstream-two failure
+check "@@{u}" upstream-two
 nonsense "@@{-1}"
 
 test_done
-- 
1.8.3.rc0.24.g6456091