pack-objects: extend --local to mean ignore non-local loose objects too

With this patch, --local means pack only local objects that are not already
packed.

Additionally, this fixes t7700 testing whether loose objects in an alternate
object database are repacked.

Signed-off-by: Brandon Casey <drafnel@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

Documentation/git-pack-objects.txt

@@ -121,7 +121,7 @@ base-name::
 --local::
 	This flag is similar to `--incremental`; instead of
 	ignoring all packed objects, it only ignores objects
-	that are packed and not in the local object store
+	that are packed and/or not in the local object store
 	(i.e. borrowed from an alternate).
 
 --non-empty::

builtin-pack-objects.c

@@ -691,6 +691,9 @@ static int add_object_entry(const unsigned char *sha1, enum object_type type,
 		return 0;
 	}
 
+	if (!exclude && local && has_loose_object_nonlocal(sha1))
+		return 0;
+
 	for (p = packed_git; p; p = p->next) {
 		off_t offset = find_pack_entry_one(sha1, p);
 		if (offset) {

t/t7700-repack.sh

@@ -34,7 +34,7 @@ test_expect_success 'objects in packs marked .keep are not repacked' '
 	test -z "$found_duplicate_object"
 '
 
-test_expect_failure 'loose objects in alternate ODB are not repacked' '
+test_expect_success 'loose objects in alternate ODB are not repacked' '
 	mkdir alt_objects &&
 	echo `pwd`/alt_objects > .git/objects/info/alternates &&
 	echo content3 > file3 &&