pack-objects: allow --shallow and --path-walk

There does not appear to be anything particularly incompatible about the
--shallow and --path-walk options of 'git pack-objects'. If shallow
commits are to be handled differently, then it is by the revision walk
that defines the commit set and which are interesting or uninteresting.

However, before the previous change, a trivial removal of the warning
would cause a failure in t5500-fetch-pack.sh when
GIT_TEST_PACK_PATH_WALK is enabled. The shallow fetch would provide more
objects than we desired, due to some incorrect behavior of the path-walk
API, especially around walking uninteresting objects.

The recently-added tests in t5538-push-shallow.sh help to confirm this
behavior is working with the --path-walk option if
GIT_TEST_PACK_PATH_WALK is enabled. These tests passed previously due to
the --path-walk feature being disabled in the presence of a shallow
clone.

Signed-off-by: Derrick Stolee <[e-mail]>
Signed-off-by: Junio C Hamano <[e-mail]>

builtin/pack-objects.c

···
 static timestamp_t unpack_unreachable_expiration;
 static int pack_loose_unreachable;
 static int cruft;
+static int shallow = 0;
 static timestamp_t cruft_expiration;
 static int local;
 static int have_non_local_packs;
···
 	 * base objects.
 	 */
 	info.prune_all_uninteresting = sparse;
+	info.edge_aggressive = shallow;
 
 	trace2_region_enter("pack-objects", "path-walk", revs->repo);
 	result = walk_objects_by_path(&info);
···
 		     struct repository *repo UNUSED)
 {
 	int use_internal_rev_list = 0;
-	int shallow = 0;
 	int all_progress_implied = 0;
 	struct strvec rp = STRVEC_INIT;
 	int rev_list_unpacked = 0, rev_list_all = 0, rev_list_reflog = 0;
···
 			option = "--filter";
 		else if (use_delta_islands)
 			option = "--delta-islands";
-		else if (shallow)
-			option = "--shallow";
 
 		if (option) {
 			warning(_("cannot use %s with %s"),

t/t5538-push-shallow.sh

···
 
 	# If the delta base is found, then this message uses "bytes".
 	# If the delta base is not found, then this message uses "KiB".
-	test_grep "Writing objects: .* bytes" err
+	test_grep "Writing objects: .* bytes" err &&
+
+	git -C deltas commit --amend -m "changed message" &&
+	GIT_TRACE2_EVENT="$(pwd)/config-push.txt" \
+	GIT_PROGRESS_DELAY=0 git -C deltas -c pack.usePathWalk=true \
+		push --progress -f origin deltas 2>err &&
+
+	test_grep "Enumerating objects: 1, done" err &&
+	test_region pack-objects path-walk config-push.txt
 '
 
 test_done