walker: let walker_say take arbitrary formats

We take a printf-style format and a single "char *"
parameter, and the format must therefore have at most one
"%s" in it. Besides being error-prone (and tickling
-Wformat-nonliteral), this is unnecessarily restrictive. We
can just provide the usual varargs interface.

Signed-off-by: Jeff King <peff@peff.net>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

walker.c

@@ -9,10 +9,14 @@
 
 static unsigned char current_commit_sha1[20];
 
-void walker_say(struct walker *walker, const char *fmt, const char *hex)
+void walker_say(struct walker *walker, const char *fmt, ...)
 {
-	if (walker->get_verbosely)
-		fprintf(stderr, fmt, hex);
+	if (walker->get_verbosely) {
+		va_list ap;
+		va_start(ap, fmt);
+		vfprintf(stderr, fmt, ap);
+		va_end(ap);
+	}
 }
 
 static void report_missing(const struct object *obj)

walker.h

@@ -19,7 +19,8 @@ struct walker {
 };
 
 /* Report what we got under get_verbosely */
-void walker_say(struct walker *walker, const char *, const char *);
+__attribute__((format (printf, 2, 3)))
+void walker_say(struct walker *walker, const char *fmt, ...);
 
 /* Load pull targets from stdin */
 int walker_targets_stdin(char ***target, const char ***write_ref);