sha1-file: make pretend_object_file() not prefetch

When pretend_object_file() is invoked with an object that does not exist
(as is the typical case), there is no need to fetch anything from the
promisor remote, because the caller already knows what the object is
supposed to contain. Therefore, suppress the fetch. (The
OBJECT_INFO_QUICK flag is added for the same reason.)

This was noticed at $DAYJOB when "blame" was run on a file that had
uncommitted modifications.

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

sha1-file.c

@@ -1589,7 +1589,8 @@ int pretend_object_file(void *buf, unsigned long len, enum object_type type,
 	struct cached_object *co;
 
 	hash_object_file(the_hash_algo, buf, len, type_name(type), oid);
-	if (has_object_file(oid) || find_cached_object(oid))
+	if (has_object_file_with_flags(oid, OBJECT_INFO_QUICK | OBJECT_INFO_SKIP_FETCH_OBJECT) ||
+	    find_cached_object(oid))
 		return 0;
 	ALLOC_GROW(cached_objects, cached_object_nr + 1, cached_object_alloc);
 	co = &cached_objects[cached_object_nr++];

t/t8002-blame.sh

@@ -122,4 +122,15 @@ test_expect_success '--exclude-promisor-objects does not BUG-crash' '
 	test_must_fail git blame --exclude-promisor-objects one
 '
 
+test_expect_success 'blame with uncommitted edits in partial clone does not crash' '
+	git init server &&
+	echo foo >server/file.txt &&
+	git -C server add file.txt &&
+	git -C server commit -m file &&
+
+	git clone --filter=blob:none "file://$(pwd)/server" client &&
+	echo bar >>client/file.txt &&
+	git -C client blame file.txt
+'
+
 test_done