[PATCH] Check packs and then files.

This reverses the order of object lookup, to check pack index first and
then go to the filesystem to find .git/objects/??/ hierarchy.

When most of the objects are packed, this saves quite many stat() calls
and negative dcache entries; while the price this approach has to pay is
negligible, even when most of the objects are outside pack, because
checking pack index file is quite cheap.

Signed-off-by: Junio C Hamano <junkio@cox.net>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>

sha1_file.c

@@ -1035,14 +1035,17 @@ void * read_sha1_file(const unsigned char *sha1, char *type, unsigned long *size
 {
 	unsigned long mapsize;
 	void *map, *buf;
+	struct pack_entry e;
 
+	if (find_pack_entry(sha1, &e))
+		return read_packed_sha1(sha1, type, size);
 	map = map_sha1_file_internal(sha1, &mapsize);
 	if (map) {
 		buf = unpack_sha1_file(map, mapsize, type, size);
 		munmap(map, mapsize);
 		return buf;
 	}
-	return read_packed_sha1(sha1, type, size);
+	return NULL;
 }
 
 void *read_object_with_reference(const unsigned char *sha1,
@@ -1343,9 +1346,9 @@ int has_sha1_file(const unsigned char *sha1)
 	struct stat st;
 	struct pack_entry e;
 
-	if (find_sha1_file(sha1, &st))
+	if (find_pack_entry(sha1, &e))
 		return 1;
-	return find_pack_entry(sha1, &e);
+	return find_sha1_file(sha1, &st) ? 1 : 0;
 }
 
 int index_fd(unsigned char *sha1, int fd, struct stat *st, int write_object, const char *type)