chmod :: FilePath -> FileMode -> IO ()
chmod path mode | mode > 0o7777 = error "FsTree.chmod: invalid mode"
                | otherwise     = setFileMode path mode
chmod :: FilePath -> FileMode -> IO ()
chmod path mode | mode > 0o7777 = error "FsTree.chmod: invalid mode"
                | otherwise     = setFileMode path mode
chmod path mode | mode > 0o7777 = error "FsTree.chmod: invalid mode"
                | otherwise     = setFileMode path mode