i18n: refactor "foo and bar are mutually exclusive"

Use static strings for constant parts of the sentences. They are all
turned into "cannot be used together".

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/range-diff.c b/range-diff.c
index cac89a2..30a4de5 100644
--- a/range-diff.c
+++ b/range-diff.c
@@ -556,7 +556,7 @@ int show_range_diff(const char *range1, const char *range2,
 	struct string_list branch2 = STRING_LIST_INIT_DUP;
 
 	if (range_diff_opts->left_only && range_diff_opts->right_only)
-		res = error(_("--left-only and --right-only are mutually exclusive"));
+		res = error(_("options '%s' and '%s' cannot be used together"), "--left-only", "--right-only");
 
 	if (!res && read_patches(range1, &branch1, range_diff_opts->other_arg))
 		res = error(_("could not parse log for '%s'"), range1);