cache-tree: do not lazy-fetch tentative tree

The cache-tree datastructure is used to speed up the comparison
between the HEAD and the index, and when the index is updated by
a cherry-pick (for example), a tree object that would represent
the paths in the index in a directory is constructed in-core, to
see if such a tree object exists already in the object store.

When the lazy-fetch mechanism was introduced, we converted this
"does the tree exist?" check into an "if it does not, and if we
lazily cloned, see if the remote has it" call by mistake.  Since
the whole point of this check is to repair the cache-tree by
recording an already existing tree object opportunistically, we
shouldn't even try to fetch one from the remote.

Pass the OBJECT_INFO_SKIP_FETCH_OBJECT flag to make sure we only
check for existence in the local object store without triggering the
lazy fetch mechanism.

Signed-off-by: Jonathan Tan <jonathantanmy@google.com>
[jc: rewritten the proposed log message]
Signed-off-by: Junio C Hamano <gitster@pobox.com>

1 files changed, 14 insertions, 0 deletions

diff --git a/t/t0410-partial-clone.sh b/t/t0410-partial-clone.sh
index 6415063..3e434b6 100755
--- a/t/t0410-partial-clone.sh
+++ b/t/t0410-partial-clone.sh
@@ -492,6 +492,20 @@ test_expect_success 'gc stops traversal when a missing but promised object is re
 	! grep "$TREE_HASH" out
 '
 
+test_expect_success 'do not fetch when checking existence of tree we construct ourselves' '
+	rm -rf repo &&
+	test_create_repo repo &&
+	test_commit -C repo base &&
+	test_commit -C repo side1 &&
+	git -C repo checkout base &&
+	test_commit -C repo side2 &&
+
+	git -C repo config core.repositoryformatversion 1 &&
+	git -C repo config extensions.partialclone "arbitrary string" &&
+
+	git -C repo cherry-pick side1
+'
+
 . "$TEST_DIRECTORY"/lib-httpd.sh
 start_httpd