object-store: rename and expand packed_git's sha1 member

This member is used to represent the pack checksum of the pack in
question.  Expand this member to be GIT_MAX_RAWSZ bytes in length so it
works with longer hashes and rename it to be "hash" instead of "sha1".
This transformation was made with a change to the definition and the
following semantic patch:

@@
struct packed_git *E1;
@@
- E1->sha1
+ E1->hash

@@
struct packed_git E1;
@@
- E1.sha1
+ E1.hash

Signed-off-by: brian m. carlson <sandals@crustytoothpaste.net>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

http-push.c

@@ -315,7 +315,8 @@ static void start_fetch_packed(struct transfer_request *request)
 		return;
 	}
 
-	fprintf(stderr,	"Fetching pack %s\n", sha1_to_hex(target->sha1));
+	fprintf(stderr,	"Fetching pack %s\n",
+		sha1_to_hex(target->hash));
 	fprintf(stderr, " which contains %s\n", oid_to_hex(&request->obj->oid));
 
 	preq = new_http_pack_request(target, repo->url);