list-objects-filter: teach tree:# how to handle >0

Implement positive values for <depth> in the tree:<depth> filter. The
exact semantics are described in Documentation/rev-list-options.txt.

The long-term goal at the end of this is to allow a partial clone to
eagerly fetch an entire directory of files by fetching a tree and
specifying <depth>=1. This, for instance, would make a build operation
fast and convenient. It is fast because the partial clone does not need
to fetch each file individually, and convenient because the user does
not need to supply a sparse-checkout specification.

Another way of considering this feature is as a way to reduce
round-trips, since the client can get any number of levels of
directories in a single request, rather than wait for each level of tree
objects to come back, whose entries are used to construct a new request.

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

1 files changed, 111 insertions, 0 deletions

diff --git a/t/t6112-rev-list-filters-objects.sh b/t/t6112-rev-list-filters-objects.sh
index eb32505a6e..706845f1d9 100755
--- a/t/t6112-rev-list-filters-objects.sh
+++ b/t/t6112-rev-list-filters-objects.sh
@@ -294,6 +294,117 @@ test_expect_success 'filter a GIANT tree through tree:0' '
 	! grep "Skipping contents of tree [^.]" filter_trace
 '
 
+# Test tree:# filters.
+
+expect_has () {
+	commit=$1 &&
+	name=$2 &&
+
+	hash=$(git -C r3 rev-parse $commit:$name) &&
+	grep "^$hash $name$" actual
+}
+
+test_expect_success 'verify tree:1 includes root trees' '
+	git -C r3 rev-list --objects --filter=tree:1 HEAD >actual &&
+
+	# We should get two root directories and two commits.
+	expect_has HEAD "" &&
+	expect_has HEAD~1 ""  &&
+	test_line_count = 4 actual
+'
+
+test_expect_success 'verify tree:2 includes root trees and immediate children' '
+	git -C r3 rev-list --objects --filter=tree:2 HEAD >actual &&
+
+	expect_has HEAD "" &&
+	expect_has HEAD~1 "" &&
+	expect_has HEAD dir1 &&
+	expect_has HEAD pattern &&
+	expect_has HEAD sparse1 &&
+	expect_has HEAD sparse2 &&
+
+	# There are also 2 commit objects
+	test_line_count = 8 actual
+'
+
+test_expect_success 'verify tree:3 includes everything expected' '
+	git -C r3 rev-list --objects --filter=tree:3 HEAD >actual &&
+
+	expect_has HEAD "" &&
+	expect_has HEAD~1 "" &&
+	expect_has HEAD dir1 &&
+	expect_has HEAD dir1/sparse1 &&
+	expect_has HEAD dir1/sparse2 &&
+	expect_has HEAD pattern &&
+	expect_has HEAD sparse1 &&
+	expect_has HEAD sparse2 &&
+
+	# There are also 2 commit objects
+	test_line_count = 10 actual
+'
+
+# Test provisional omit collection logic with a repo that has objects appearing
+# at multiple depths - first deeper than the filter's threshold, then shallow.
+
+test_expect_success 'setup r4' '
+	git init r4 &&
+
+	echo foo > r4/foo &&
+	mkdir r4/subdir &&
+	echo bar > r4/subdir/bar &&
+
+	mkdir r4/filt &&
+	cp -r r4/foo r4/subdir r4/filt &&
+
+	git -C r4 add foo subdir filt &&
+	git -C r4 commit -m "commit msg"
+'
+
+expect_has_with_different_name () {
+	repo=$1 &&
+	name=$2 &&
+
+	hash=$(git -C $repo rev-parse HEAD:$name) &&
+	! grep "^$hash $name$" actual &&
+	grep "^$hash " actual &&
+	! grep "~$hash" actual
+}
+
+test_expect_success 'test tree:# filter provisional omit for blob and tree' '
+	git -C r4 rev-list --objects --filter-print-omitted --filter=tree:2 \
+		HEAD >actual &&
+	expect_has_with_different_name r4 filt/foo &&
+	expect_has_with_different_name r4 filt/subdir
+'
+
+# Test tree:<depth> where a tree is iterated to twice - once where a subentry is
+# too deep to be included, and again where the blob inside it is shallow enough
+# to be included. This makes sure we don't use LOFR_MARK_SEEN incorrectly (we
+# can't use it because a tree can be iterated over again at a lower depth).
+
+test_expect_success 'tree:<depth> where we iterate over tree at two levels' '
+	git init r5 &&
+
+	mkdir -p r5/a/subdir/b &&
+	echo foo > r5/a/subdir/b/foo &&
+
+	mkdir -p r5/subdir/b &&
+	echo foo > r5/subdir/b/foo &&
+
+	git -C r5 add a subdir &&
+	git -C r5 commit -m "commit msg" &&
+
+	git -C r5 rev-list --objects --filter=tree:4 HEAD >actual &&
+	expect_has_with_different_name r5 a/subdir/b/foo
+'
+
+test_expect_success 'tree:<depth> which filters out blob but given as arg' '
+	blob_hash=$(git -C r4 rev-parse HEAD:subdir/bar) &&
+
+	git -C r4 rev-list --objects --filter=tree:1 HEAD $blob_hash >actual &&
+	grep ^$blob_hash actual
+'
+
 # Delete some loose objects and use rev-list, but WITHOUT any filtering.
 # This models previously omitted objects that we did not receive.