Squelch overzealous "ignoring dangling symref" in an empty repository

057e7138 (Warn use of "origin" when remotes/origin/HEAD is dangling,
2009-02-08) tried to warn dangling refs/remotes/origin/HEAD only when
"origin" was used to refer to it.  There was one corner case a symref is
expected to be dangling and this warning is unwarranted: HEAD in an empty
repository.

This squelches the warning for this special case.
Signed-off-by: NJunio C Hamano <gitster@pobox.com>

sha1_name.c

@@ -278,7 +278,8 @@ int dwim_ref(const char *str, int len, unsigned char *sha1, char **ref)
 				*ref = xstrdup(r);
 			if (!warn_ambiguous_refs)
 				break;
-		} else if (flag & REF_ISSYMREF)
+		} else if ((flag & REF_ISSYMREF) &&
+			   (len != 4 || strcmp(str, "HEAD")))
 			warning("ignoring dangling symref %s.", fullref);
 	}
 	free(last_branch);