i18n: factorize "--foo requires --bar" and the like

They are all replaced by "the option '%s' requires '%s'", which is a
new string but replaces 17 previous unique strings.

Signed-off-by: Jean-Noël Avila <jn.avila@free.fr>
Reviewed-by: Johannes Sixt <j6t@kdbg.org>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
diff --git a/builtin/checkout.c b/builtin/checkout.c
index 73f5a6f..af5fa82 100644
--- a/builtin/checkout.c
+++ b/builtin/checkout.c
@@ -1758,7 +1758,7 @@ static int checkout_main(int argc, const char **argv, const char *prefix,
 				    0,
 				    prefix, opts->pathspec_from_file, opts->pathspec_file_nul);
 	} else if (opts->pathspec_file_nul) {
-		die(_("--pathspec-file-nul requires --pathspec-from-file"));
+		die(_("the option '%s' requires '%s'"), "--pathspec-file-nul", "--pathspec-from-file");
 	}
 
 	opts->pathspec.recursive = 1;