verify-pack: use strbuf_strip_suffix

In this code, we try to convert both "foo.idx" and "foo"
into "foo.pack". By stripping the suffix, we can avoid a
confusing use of strbuf_splice, and make it clear that both
cases are adding ".pack" to the end.

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

builtin/verify-pack.c

@@ -27,10 +27,9 @@ static int verify_one_pack(const char *path, unsigned int flags)
 	 * normalize these forms to "foo.pack" for "index-pack --verify".
 	 */
 	strbuf_addstr(&arg, path);
-	if (ends_with(arg.buf, ".idx"))
-		strbuf_splice(&arg, arg.len - 3, 3, "pack", 4);
-	else if (!ends_with(arg.buf, ".pack"))
-		strbuf_add(&arg, ".pack", 5);
+	if (strbuf_strip_suffix(&arg, ".idx") ||
+	    !ends_with(arg.buf, ".pack"))
+		strbuf_addstr(&arg, ".pack");
 	argv[2] = arg.buf;
 
 	memset(&index_pack, 0, sizeof(index_pack));