fsck: report trees as dangling

After checking connectivity, fsck looks through the list of
any objects we've seen mentioned, and reports unreachable
and un-"used" ones as dangling. However, it skips any object
which is not marked as "parsed", as that is an object that
we _don't_ have (but that somebody mentioned).

Since 6e454b9 (clear parsed flag when we free tree
buffers, 2013-06-05), that flag can't be relied on, and the
correct method is to check the HAS_OBJ flag. The cleanup in
that commit missed this callsite, though. As a result, we
would generally fail to report dangling trees.

We never noticed because there were no tests in this area
(for trees or otherwise). Let's add some.

Signed-off-by: Jeff King <peff@peff.net>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

builtin/fsck.c

@@ -225,7 +225,7 @@ static void check_unreachable_object(struct object *obj)
 	 * to complain about it being unreachable (since it does
 	 * not exist).
 	 */
-	if (!obj->parsed)
+	if (!(obj->flags & HAS_OBJ))
 		return;
 
 	/*

t/t1450-fsck.sh

@@ -559,4 +559,31 @@ test_expect_success 'fsck --name-objects' '
 	)
 '
 
+# for each of type, we have one version which is referenced by another object
+# (and so while unreachable, not dangling), and another variant which really is
+# dangling.
+test_expect_success 'fsck notices dangling objects' '
+	git init dangling &&
+	(
+		cd dangling &&
+		blob=$(echo not-dangling | git hash-object -w --stdin) &&
+		dblob=$(echo dangling | git hash-object -w --stdin) &&
+		tree=$(printf "100644 blob %s\t%s\n" $blob one | git mktree) &&
+		dtree=$(printf "100644 blob %s\t%s\n" $blob two | git mktree) &&
+		commit=$(git commit-tree $tree) &&
+		dcommit=$(git commit-tree -p $commit $tree) &&
+
+		cat >expect <<-EOF &&
+		dangling blob $dblob
+		dangling commit $dcommit
+		dangling tree $dtree
+		EOF
+
+		git fsck >actual &&
+		# the output order is non-deterministic, as it comes from a hash
+		sort <actual >actual.sorted &&
+		test_cmp expect actual.sorted
+	)
+'
+
 test_done