Add test to rename into root directory

The ancestor tests in rename were preventing renaming into the root
directory.

Signed-off-by: Zach Brown <zab@versity.com>

kmod/src/dir.c

@@ -1443,6 +1443,11 @@ static int item_d_ancestor(struct super_block *sb, u64 p1, u64 p2, u64 *p_ret)
 
 	*p_ret = 0;
 
+	if (p2 == SCOUTFS_ROOT_INO) {
+		ret = 0;
+		goto out;
+	}
+
 	ret = scoutfs_dir_get_backref_path(sb, p2, 0, 0, &list);
 	if (ret)
 		goto out;

tests/golden/basic-posix-consistency

@@ -49,6 +49,7 @@ four
 --- can't overwrite non-empty dir
 mv: cannot move ‘/mnt/test/test/basic-posix-consistency/dir/c/clobber’ to ‘/mnt/test/test/basic-posix-consistency/dir/a/dir’: Directory not empty
 --- can overwrite empty dir
+--- can rename into root
 == path resoluion
 == inode indexes match after syncing existing
 == inode indexes match after copying and syncing

tests/tests/basic-posix-consistency.sh

@@ -149,6 +149,10 @@ find "$T_D0/dir" -ls 2>&1 | t_filter_fs > "$T_TMP.0"
 find "$T_D1/dir" -ls 2>&1 | t_filter_fs > "$T_TMP.1"
 diff -u "$T_TMP.0" "$T_TMP.1"
 rm -rf "$T_D0/dir"
+echo "--- can rename into root"
+touch "$T_D0/rename-into-root"
+mv "$T_D0/rename-into-root" "$T_M0/"
+rm -f "$T_M0/rename-into-root"
 
 echo "== path resoluion"
 touch "$T_D0/file"