create_symref: if symlink fails, fall back to writing a "symbolic ref"

There are filesystems out there which do not understand symlinks, even if
the OS is perfectly capable of writing them. So, do not fail right away,
but try to write a symbolic ref first. If that fails, you can die().

Signed-off-by: Johannes Schindelin <Johannes.Schindelin@gmx.de>
Signed-off-by: Junio C Hamano <junkio@cox.net>

refs.c

@@ -116,14 +116,17 @@ const char *resolve_ref(const char *path, unsigned char *sha1, int reading)
 
 int create_symref(const char *git_HEAD, const char *refs_heads_master)
 {
-#if USE_SYMLINK_HEAD
-	unlink(git_HEAD);
-	return symlink(refs_heads_master, git_HEAD);
-#else
 	const char *lockpath;
 	char ref[1000];
 	int fd, len, written;
 
+#if USE_SYMLINK_HEAD
+	unlink(git_HEAD);
+	if (!symlink(refs_heads_master, git_HEAD))
+		return 0;
+	fprintf(stderr, "no symlink - falling back to symbolic ref\n");
+#endif
+
 	len = snprintf(ref, sizeof(ref), "ref: %s\n", refs_heads_master);
 	if (sizeof(ref) <= len) {
 		error("refname too long: %s", refs_heads_master);
@@ -144,7 +147,6 @@ int create_symref(const char *git_HEAD, const char *refs_heads_master)
 		return -3;
 	}
 	return 0;
-#endif
 }
 
 int read_ref(const char *filename, unsigned char *sha1)