bookmarks: always write undo file Always write the undo file. Otherwise, rollback will not work for the initial bookmark as undo.bookmarks doesn't exists. In this case undo.bookmarks needs already be empty.

opener: force copy on 'a'ppend if nlinks() returns 0 (issue1922) If pywin32 is not installed, 'os.lstat(pathname).st_nlink' is used for nlinks(), which is always zero for all files on Windows. To make sure we break up hardlinks if pywin32 is missing, we force nlink = 2 if nlinks() returns < 1. (this completely fixes issue1922)