Merge branch 'jt/cache-tree-allow-missing-object-in-partial-clone'

In a partial clone that will lazily be hydrated from the
originating repository, we generally want to avoid "does this
object exist (locally)?" on objects that we deliberately omitted
when we created the clone.  The cache-tree codepath (which is used
to write a tree object out of the index) however insisted that the
object exists, even for paths that are outside of the partial
checkout area.  The code has been updated to avoid such a check.

* jt/cache-tree-allow-missing-object-in-partial-clone:
  cache-tree: skip some blob checks in partial clone

Author: gitster

cache-tree.c

@@ -326,6 +326,7 @@ static int update_one(struct cache_tree *it,
 		unsigned mode;
 		int expected_missing = 0;
 		int contains_ita = 0;
+		int ce_missing_ok;
 
 		path = ce->name;
 		pathlen = ce_namelen(ce);
@@ -355,8 +356,11 @@ static int update_one(struct cache_tree *it,
 			i++;
 		}
 
+		ce_missing_ok = mode == S_IFGITLINK || missing_ok ||
+			(repository_format_partial_clone &&
+			 ce_skip_worktree(ce));
 		if (is_null_oid(oid) ||
-		    (mode != S_IFGITLINK && !missing_ok && !has_object_file(oid))) {
+		    (!ce_missing_ok && !has_object_file(oid))) {
 			strbuf_release(&buffer);
 			if (expected_missing)
 				return -1;

t/t1090-sparse-checkout-scope.sh

@@ -63,4 +63,37 @@ test_expect_success 'return to full checkout of master' '
 	test "$(cat b)" = "modified"
 '
 
+test_expect_success 'in partial clone, sparse checkout only fetches needed blobs' '
+	test_create_repo server &&
+	git clone "file://$(pwd)/server" client &&
+
+	test_config -C server uploadpack.allowfilter 1 &&
+	test_config -C server uploadpack.allowanysha1inwant 1 &&
+	echo a >server/a &&
+	echo bb >server/b &&
+	mkdir server/c &&
+	echo ccc >server/c/c &&
+	git -C server add a b c/c &&
+	git -C server commit -m message &&
+
+	test_config -C client core.sparsecheckout 1 &&
+	test_config -C client extensions.partialclone origin &&
+	echo "!/*" >client/.git/info/sparse-checkout &&
+	echo "/a" >>client/.git/info/sparse-checkout &&
+	git -C client fetch --filter=blob:none origin &&
+	git -C client checkout FETCH_HEAD &&
+
+	git -C client rev-list HEAD \
+		--quiet --objects --missing=print >unsorted_actual &&
+	(
+		printf "?" &&
+		git hash-object server/b &&
+		printf "?" &&
+		git hash-object server/c/c
+	) >unsorted_expect &&
+	sort unsorted_actual >actual &&
+	sort unsorted_expect >expect &&
+	test_cmp expect actual
+'
+
 test_done