Subject: [PATCH] The patch below reminded me of something:

  +               /* We want to allow .git/description file and
  +                * "description" branch to exist at the same time.
  +                * "git-rev-parse description" should silently skip
  +                * .git/description file as a candidate for
  +                * get_sha1().  However, having garbage file anywhere
  +                * under refs/ is not OK, and we would not have caught
  +                * ambiguous heads and tags with the above test.
  +                */
  +               else if (**p && !access(pathname, F_OK)) {
  +                       /* Garbage exists under .git/refs */
  +                       return error("garbage ref found '%s'", pathname);
  +               }

Maybe we should only allow only a strictly defined set of refnames under $GIT_DIR? The directory is used pretty much for anything else (temporary message files, config, description).

So, if we, say, allow only HEAD, ORIG_HEAD, and MERGE_HEAD to be references in .git/ and ignore everything else. Then there will be no ambiguity anymore and no need to parse "description" or "config" reference (besides, I can very simply imagine a message file containing "ref: refs/heads/foo").

Does it make sense or have I missed some very informative discussion as to why we do allow references to be anywhere in .git?

---

 sha1_name.c |   22 +++++++++++++++++++++-
 1 files changed, 21 insertions(+), 1 deletions(-)

4a0ef1ed775d2311da7125257cb734d561fd2ef1
diff --git a/sha1_name.c b/sha1_name.c
index bf8f0f0..dce1574 100644
--- a/sha1_name.c
+++ b/sha1_name.c
@@ -247,7 +247,27 @@ static int get_sha1_basic(const char *st
 	if (ambiguous_path(str, len))
 		return -1;
 
-	for (p = prefix; *p; p++) {
+	p = prefix;
+	/* Check references _without_ leading directories */
+	if (!memchr(str, '/', len)) {
+		/* only these references can be directly in $GIT_DIR... */
+		static const char *git_refs[] = {
+			"HEAD",
+			"ORIG_HEAD",
+			"FETCH_HEAD",
+			"MERGE_HEAD",
+			NULL
+		};
+		const char **r;
+		for (r = git_refs; *r; ++r)
+			if (strlen(*r) == len && strncmp(*r, str, len) == 0)
+				break;
+		/* ...all the others have to be somewhere under .git/refs/ */
+		if ( !*r )
+			++p;
+	}
+
+	for (; *p; p++) {
 		char *pathname = git_path("%s/%.*s", *p, len, str);
 
 		if (!read_ref(pathname, sha1)) {
-- 
0.99.9.GIT