Add git-symbolic-ref

This adds the counterpart of git-update-ref that lets you read
and create "symbolic refs".  By default it uses a symbolic link
to represent ".git/HEAD -> refs/heads/master", but it can be compiled
to use the textfile symbolic ref.

The places that did 'readlink .git/HEAD' and 'ln -s refs/heads/blah
.git/HEAD' have been converted to use new git-symbolic-ref command, so
that they can deal with either implementation.

Signed-off-by: Junio C Hamano <junio@twinsun.com>

1 files changed, 10 insertions, 18 deletions

diff --git a/fsck-objects.c b/fsck-objects.c
index 247edf0529..65cec7d12b 100644
--- a/fsck-objects.c
+++ b/fsck-objects.c
@@ -402,25 +402,17 @@ static void fsck_object_dir(const char *path)
 
 static int fsck_head_link(void)
 {
-	int fd, count;
-	char hex[40];
 	unsigned char sha1[20];
-	static char path[PATH_MAX], link[PATH_MAX];
-	const char *git_dir = get_git_dir();
-
-	snprintf(path, sizeof(path), "%s/HEAD", git_dir);
-	if (readlink(path, link, sizeof(link)) < 0)
-		return error("HEAD is not a symlink");
-	if (strncmp("refs/heads/", link, 11))
-		return error("HEAD points to something strange (%s)", link);
-	fd = open(path, O_RDONLY);
-	if (fd < 0)
-		return error("HEAD: %s", strerror(errno));
-	count = read(fd, hex, sizeof(hex));
-	close(fd);
-	if (count < 0)
-		return error("HEAD: %s", strerror(errno));
-	if (count < 40 || get_sha1_hex(hex, sha1))
+	const char *git_HEAD = strdup(git_path("HEAD"));
+	const char *git_refs_heads_master = resolve_ref(git_HEAD, sha1, 1);
+	int pfxlen = strlen(git_HEAD) - 4; /* strip .../.git/ part */
+
+	if (!git_refs_heads_master)
+		return error("HEAD is not a symbolic ref");
+	if (strncmp(git_refs_heads_master + pfxlen, "refs/heads/", 11))
+		return error("HEAD points to something strange (%s)",
+			     git_refs_heads_master + pfxlen);
+	if (!memcmp(null_sha1, sha1, 20))
 		return error("HEAD: not a valid git pointer");
 	return 0;
 }