Merge branch 'jk/virtual-objects-do-exist'

A recent update broke "is this object available to us?" check for
well-known objects like an empty tree (which should yield "yes",
even when there is no on-disk object for an empty tree), which has
been corrected.

* jk/virtual-objects-do-exist:
  rev-list: allow cached objects in existence check

Author: gitster

builtin/rev-list.c

@@ -238,7 +238,7 @@ static inline void finish_object__ma(struct object *obj)
 static int finish_object(struct object *obj, const char *name, void *cb_data)
 {
 	struct rev_list_info *info = cb_data;
-	if (!has_object_file(&obj->oid)) {
+	if (oid_object_info_extended(the_repository, &obj->oid, NULL, 0) < 0) {
 		finish_object__ma(obj);
 		return 1;
 	}

t/t1060-object-corruption.sh

@@ -127,4 +127,14 @@ test_expect_success 'fetch into corrupted repo with index-pack' '
 	)
 '
 
+test_expect_success 'internal tree objects are not "missing"' '
+	git init missing-empty &&
+	(
+		cd missing-empty &&
+		empty_tree=$(git hash-object -t tree /dev/null) &&
+		commit=$(echo foo | git commit-tree $empty_tree) &&
+		git rev-list --objects $commit
+	)
+'
+
 test_done