show-branch: handle [] globs as well.

Earlier only '?' and '*' signalled the command that what the
user has given is a glob pattern.  This prevented us to say:

	$ git show-branch 'v0.99.[0-3]'

Now we notice '[' as well, so the above would work.
Signed-off-by: NJunio C Hamano <junkio@cox.net>

show-branch.c

@@ -492,7 +492,7 @@ static void append_one_rev(const char *av)
 		append_ref(av, revkey);
 		return;
 	}
-	if (strchr(av, '*') || strchr(av, '?')) {
+	if (strchr(av, '*') || strchr(av, '?') || strchr(av, '[')) {
 		/* glob style match */
 		int saved_matches = ref_name_cnt;
 		match_ref_pattern = av;