get_sha1_basic(): try refs/... and finally refs/remotes/$foo/HEAD

This implements the suggestion by Jeff King to use
refs/remotes/$foo/HEAD to interpret a shorthand "$foo" to mean
the primary branch head of a tracked remote.  clone needs to be
told about this convention as well.

Signed-off-by: Junio C Hamano <junkio@cox.net>

diff --git a/sha1_name.c b/sha1_name.c
index 74c479c..3adaec3 100644 (file)
--- a/sha1_name.c
+++ b/sha1_name.c
@@ -235,18 +235,21 @@ static int ambiguous_path(const char *path, int len)
 
 static int get_sha1_basic(const char *str, int len, unsigned char *sha1)
 {
-       static const char *prefix[] = {
-               "",
-               "refs",
-               "refs/tags",
-               "refs/heads",
-               "refs/remotes",
+       static const char *fmt[] = {
+               "/%.*s",
+               "refs/%.*s",
+               "refs/tags/%.*s",
+               "refs/heads/%.*s",
+               "refs/remotes/%.*s",
+               "refs/remotes/%.*s/HEAD",
                NULL
        };
        const char **p;
        const char *warning = "warning: refname '%.*s' is ambiguous.\n";
        char *pathname;
        int already_found = 0;
+       unsigned char *this_result;
+       unsigned char sha1_from_ref[20];
 
        if (len == 40 && !get_sha1_hex(str, sha1))
                return 0;
@@ -255,11 +258,9 @@ static int get_sha1_basic(const char *str, int len, unsigned char *sha1)
        if (ambiguous_path(str, len))
                return -1;
 
-       for (p = prefix; *p; p++) {
-               unsigned char sha1_from_ref[20];
-               unsigned char *this_result =
-                       already_found ? sha1_from_ref : sha1;
-               pathname = git_path("%s/%.*s", *p, len, str);
+       for (p = fmt; *p; p++) {
+               this_result = already_found ? sha1_from_ref : sha1;
+               pathname = git_path(*p, len, str);
                if (!read_ref(pathname, this_result)) {
                        if (warn_ambiguous_refs) {
                                if (already_found &&