sha1_file: freshen pack objects before loose

When writing out an object file, we first check whether it
already exists and if so optimize out the write. Prior to
33d4221, we did this by calling has_sha1_file(), which will
check for packed objects followed by loose. Since that
commit, we check loose objects first.

For the common case of a repository whose objects are mostly
packed, this means we will make a lot of extra access()
system calls checking for loose objects. We should follow
the same packed-then-loose order that all of our other
lookups use.

Reported-by: Stefan Saasen <ssaasen@atlassian.com>
Signed-off-by: Jeff King <peff@peff.net>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

sha1_file.c

@@ -3014,7 +3014,7 @@ int write_sha1_file(const void *buf, unsigned long len, const char *type, unsign
 	write_sha1_file_prepare(buf, len, type, sha1, hdr, &hdrlen);
 	if (returnsha1)
 		hashcpy(returnsha1, sha1);
-	if (freshen_loose_object(sha1) || freshen_packed_object(sha1))
+	if (freshen_packed_object(sha1) || freshen_loose_object(sha1))
 		return 0;
 	return write_loose_object(sha1, hdr, hdrlen, buf, len, 0);
 }