Fix "unpack-objects --strict"

When unpack-objects is run under the --strict option, objects that have
pointers to other objects are verified for the reachability at the end, by
calling check_object() on each of them, and letting check_object to walk
the reachable objects from them using fsck_walk() recursively.

The function however misunderstands the semantics of fsck_walk() function
when it makes a call to it, setting itself as the callback.  fsck_walk()
expects the callback function to return a non-zero value to signal an
error (negative value causes an immediate abort, positive value is still
an error but allows further checks on sibling objects) and return zero to
signal a success.  The function however returned 1 on some non error
cases, and to cover up this mistake, complained only when fsck_walk() did
not detect any error.

To fix this double-bug, make the function return zero on all success
cases, and also check for non-zero return from fsck_walk() for an error.

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

builtin-unpack-objects.c

@@ -181,10 +181,10 @@ static void write_cached_object(struct object *obj)
 static int check_object(struct object *obj, int type, void *data)
 {
 	if (!obj)
-		return 0;
+		return 1;
 
 	if (obj->flags & FLAG_WRITTEN)
-		return 1;
+		return 0;
 
 	if (type != OBJ_ANY && obj->type != type)
 		die("object type mismatch");
@@ -195,22 +195,24 @@ static int check_object(struct object *obj, int type, void *data)
 		if (type != obj->type || type <= 0)
 			die("object of unexpected type");
 		obj->flags |= FLAG_WRITTEN;
-		return 1;
+		return 0;
 	}
 
 	if (fsck_object(obj, 1, fsck_error_function))
 		die("Error in object");
-	if (!fsck_walk(obj, check_object, 0))
+	if (fsck_walk(obj, check_object, 0))
 		die("Error on reachable objects of %s", sha1_to_hex(obj->sha1));
 	write_cached_object(obj);
-	return 1;
+	return 0;
 }
 
 static void write_rest(void)
 {
 	unsigned i;
-	for (i = 0; i < nr_objects; i++)
-		check_object(obj_list[i].obj, OBJ_ANY, 0);
+	for (i = 0; i < nr_objects; i++) {
+		if (obj_list[i].obj)
+			check_object(obj_list[i].obj, OBJ_ANY, 0);
+	}
 }
 
 static void added_object(unsigned nr, enum object_type type,

t/t5531-deep-submodule-push.sh

@@ -0,0 +1,35 @@
+#!/bin/sh
+
+test_description='unpack-objects'
+
+. ./test-lib.sh
+
+test_expect_success setup '
+	mkdir pub.git &&
+	GIT_DIR=pub.git git init --bare
+	GIT_DIR=pub.git git config receive.fsckobjects true &&
+	mkdir work &&
+	(
+		cd work &&
+		git init &&
+		mkdir -p gar/bage &&
+		(
+			cd gar/bage &&
+			git init &&
+			>junk &&
+			git add junk &&
+			git commit -m "Initial junk"
+		) &&
+		git add gar/bage &&
+		git commit -m "Initial superproject"
+	)
+'
+
+test_expect_success push '
+	(
+		cd work &&
+		git push ../pub.git master
+	)
+'
+
+test_done