rev-list --verify-object

Often we want to verify everything reachable from a given set of commits
are present in our repository and connected without a gap to the tips of
our refs. We used to do this for this purpose:

    $ rev-list --objects $commits_to_be_tested --not --all

Even though this is good enough for catching missing commits and trees,
we show the object name but do not verify their existence, let alone their
well-formedness, for the blob objects at the leaf level.

Add a new "--verify-object" option so that we can catch missing and broken
blobs as well.

Signed-off-by: Junio C Hamano <gitster@pobox.com>

builtin/rev-list.c

@@ -180,7 +180,11 @@ static void show_object(struct object *obj,
 			const struct name_path *path, const char *component,
 			void *cb_data)
 {
+	struct rev_info *info = cb_data;
+
 	finish_object(obj, path, component, cb_data);
+	if (info->verify_objects && !obj->parsed && obj->type != OBJ_COMMIT)
+		parse_object(obj->sha1);
 	show_object_with_name(stdout, obj, path, component);
 }