i18n: factorize "invalid value" messages

Use the same message when an invalid value is passed to a command line
option or a configuration variable.

Signed-off-by: Jean-Noël Avila <jn.avila@free.fr>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

builtin/fetch.c

@@ -763,8 +763,8 @@ static void prepare_format_display(struct ref *ref_map)
 	else if (!strcasecmp(format, "compact"))
 		compact_format = 1;
 	else
-		die(_("configuration fetch.output contains invalid value %s"),
-		    format);
+		die(_("invalid value for '%s': '%s'"),
+		    "fetch.output", format);
 
 	for (rm = ref_map; rm; rm = rm->next) {
 		if (rm->status == REF_STATUS_REJECT_SHALLOW ||