for-each-ref: use skip_prefix() to avoid duplicate string comparison

Use skip_prefix() to get the part after "color:" (if present) and only
compare it with "reset" instead of comparing the whole string again.
This gets rid of the duplicate "color:" part of the string constant.

Signed-off-by: Rene Scharfe <l.s.r@web.de>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

builtin/for-each-ref.c

@@ -180,11 +180,10 @@ static const char *find_next(const char *cp)
 static int verify_format(const char *format)
 {
 	const char *cp, *sp;
-	static const char color_reset[] = "color:reset";
 
 	need_color_reset_at_eol = 0;
 	for (cp = format; *cp && (sp = find_next(cp)); ) {
-		const char *ep = strchr(sp, ')');
+		const char *color, *ep = strchr(sp, ')');
 		int at;
 
 		if (!ep)
@@ -193,8 +192,8 @@ static int verify_format(const char *format)
 		at = parse_atom(sp + 2, ep);
 		cp = ep + 1;
 
-		if (starts_with(used_atom[at], "color:"))
-			need_color_reset_at_eol = !!strcmp(used_atom[at], color_reset);
+		if (skip_prefix(used_atom[at], "color:", &color))
+			need_color_reset_at_eol = !!strcmp(color, "reset");
 	}
 	return 0;
 }