list-objects-filter: implement filter tree:0

Teach list-objects the "tree:0" filter which allows for filtering
out all tree and blob objects (unless other objects are explicitly
specified by the user). The purpose of this patch is to allow smaller
partial clones.

The name of this filter - tree:0 - does not explicitly specify that
it also filters out all blobs, but this should not cause much confusion
because blobs are not at all useful without the trees that refer to
them.

I also considered only:commits as a name, but this is inaccurate because
it suggests that annotated tags are omitted, but actually they are
included.

The name "tree:0" allows later filtering based on depth, i.e. "tree:1"
would filter out all but the root tree and blobs. In order to avoid
confusion between 0 and capital O, the documentation was worded in a
somewhat round-about way that also hints at this future improvement to
the feature.

Signed-off-by: Matthew DeVore <matvore@google.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

1 files changed, 42 insertions, 0 deletions

diff --git a/t/t5616-partial-clone.sh b/t/t5616-partial-clone.sh
index bbbe7537df..53fbf7db88 100755
--- a/t/t5616-partial-clone.sh
+++ b/t/t5616-partial-clone.sh
@@ -154,6 +154,48 @@ test_expect_success 'partial clone with transfer.fsckobjects=1 uses index-pack -
 	grep "git index-pack.*--fsck-objects" trace
 '
 
+test_expect_success 'use fsck before and after manually fetching a missing subtree' '
+	# push new commit so server has a subtree
+	mkdir src/dir &&
+	echo "in dir" >src/dir/file.txt &&
+	git -C src add dir/file.txt &&
+	git -C src commit -m "file in dir" &&
+	git -C src push -u srv master &&
+	SUBTREE=$(git -C src rev-parse HEAD:dir) &&
+
+	rm -rf dst &&
+	git clone --no-checkout --filter=tree:0 "file://$(pwd)/srv.bare" dst &&
+	git -C dst fsck &&
+
+	# Make sure we only have commits, and all trees and blobs are missing.
+	git -C dst rev-list --missing=allow-any --objects master \
+		>fetched_objects &&
+	awk -f print_1.awk fetched_objects |
+	xargs -n1 git -C dst cat-file -t >fetched_types &&
+
+	sort -u fetched_types >unique_types.observed &&
+	echo commit >unique_types.expected &&
+	test_cmp unique_types.expected unique_types.observed &&
+
+	# Auto-fetch a tree with cat-file.
+	git -C dst cat-file -p $SUBTREE >tree_contents &&
+	grep file.txt tree_contents &&
+
+	# fsck still works after an auto-fetch of a tree.
+	git -C dst fsck &&
+
+	# Auto-fetch all remaining trees and blobs with --missing=error
+	git -C dst rev-list --missing=error --objects master >fetched_objects &&
+	test_line_count = 70 fetched_objects &&
+
+	awk -f print_1.awk fetched_objects |
+	xargs -n1 git -C dst cat-file -t >fetched_types &&
+
+	sort -u fetched_types >unique_types.observed &&
+	printf "blob\ncommit\ntree\n" >unique_types.expected &&
+	test_cmp unique_types.expected unique_types.observed
+'
+
 test_expect_success 'partial clone fetches blobs pointed to by refs even if normally filtered out' '
 	rm -rf src dst &&
 	git init src &&