merge-recursive: separate message for common ancestors

The function "merge_recursive" prints the count of common ancestors
as "found %u common ancestor(s):".  We should use a singular and a
plural form of this message to help translators.

Signed-off-by: Ralf Thielow <ralf.thielow@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

merge-recursive.c

@@ -1915,7 +1915,10 @@ int merge_recursive(struct merge_options *o,
 	}
 
 	if (show(o, 5)) {
-		output(o, 5, _("found %u common ancestor(s):"), commit_list_count(ca));
+		unsigned cnt = commit_list_count(ca);
+
+		output(o, 5, Q_("found %u common ancestor:",
+				"found %u common ancestors:", cnt), cnt);
 		for (iter = ca; iter; iter = iter->next)
 			output_commit_title(o, iter->item);
 	}