list-objects: implement object type filter

While it already is possible to filter objects by some criteria in
git-rev-list(1), it is not yet possible to filter out only a specific
type of objects. This makes some filters less useful. The `blob:limit`
filter for example filters blobs such that only those which are smaller
than the given limit are returned. But it is unfit to ask only for these
smallish blobs, given that git-rev-list(1) will continue to print tags,
commits and trees.

Now that we have the infrastructure in place to also filter tags and
commits, we can improve this situation by implementing a new filter
which selects objects based on their type. Above query can thus
trivially be implemented with the following command:

    $ git rev-list --objects --filter=object:type=blob \
        --filter=blob:limit=200

Furthermore, this filter allows to optimize for certain other cases: if
for example only tags or commits have been selected, there is no need to
walk down trees.

The new filter is not yet supported in bitmaps. This is going to be
implemented in a subsequent commit.

Signed-off-by: Patrick Steinhardt <ps@pks.im>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

1 files changed, 44 insertions, 0 deletions

diff --git a/t/t6112-rev-list-filters-objects.sh b/t/t6112-rev-list-filters-objects.sh
index 31457d1..c810a62 100755
--- a/t/t6112-rev-list-filters-objects.sh
+++ b/t/t6112-rev-list-filters-objects.sh
@@ -159,6 +159,50 @@ test_expect_success 'verify blob:limit=1m' '
 	test_must_be_empty observed
 '
 
+# Test object:type=<type> filter.
+
+test_expect_success 'setup object-type' '
+	test_create_repo object-type &&
+	test_commit --no-tag -C object-type message blob &&
+	git -C object-type tag tag -m tag-message
+'
+
+test_expect_success 'verify object:type= fails with invalid type' '
+	test_must_fail git -C object-type rev-list --objects --filter=object:type= HEAD &&
+	test_must_fail git -C object-type rev-list --objects --filter=object:type=invalid HEAD
+'
+
+test_expect_success 'verify object:type=blob prints blob and commit' '
+	git -C object-type rev-parse HEAD >expected &&
+	printf "%s blob\n" $(git -C object-type rev-parse HEAD:blob) >>expected &&
+	git -C object-type rev-list --objects --filter=object:type=blob HEAD >actual &&
+	test_cmp expected actual
+'
+
+test_expect_success 'verify object:type=tree prints tree and commit' '
+	(
+		git -C object-type rev-parse HEAD &&
+		printf "%s \n" $(git -C object-type rev-parse HEAD^{tree})
+	) >expected &&
+	git -C object-type rev-list --objects --filter=object:type=tree HEAD >actual &&
+	test_cmp expected actual
+'
+
+test_expect_success 'verify object:type=commit prints commit' '
+	git -C object-type rev-parse HEAD >expected &&
+	git -C object-type rev-list --objects --filter=object:type=commit HEAD >actual &&
+	test_cmp expected actual
+'
+
+test_expect_success 'verify object:type=tag prints tag' '
+	(
+		git -C object-type rev-parse HEAD &&
+		printf "%s tag\n" $(git -C object-type rev-parse tag)
+	) >expected &&
+	git -C object-type rev-list --objects --filter=object:type=tag tag >actual &&
+	test_cmp expected actual
+'
+
 # Test sparse:path=<path> filter.
 # !!!!
 # NOTE: sparse:path filter support has been dropped for security reasons,