2650         # This only exist to deal with the need of rollback to have viable

  2651         # parents at the end of the operation. So backup viable parents at the

  2652         # time of this operation.

  2653         #

  2654         # We only do it when the `wlock` is taken, otherwise other might be

  2655         # altering the dirstate under us.

  2656         #

  2657         # This is really not a great way to do this (first, because we cannot

  2658         # always do it). There are more viable alternative that exists

  2659         #

  2660         # - backing only the working copy parent in a dedicated files and doing

  2661         #   a clean "keep-update" to them on `hg rollback`.

  2662         #

  2663         # - slightly changing the behavior an applying a logic similar to "hg

  2664         # strip" to pick a working copy destination on `hg rollback`

  2665         if self.currentwlock() is not None:

  2666             ds = self.dirstate

  2667 

  2668             def backup_dirstate(tr):

  2669                 for f in ds.all_file_names():

  2670                     # hardlink backup is okay because `dirstate` is always

  2671                     # atomically written and possible data file are append only

  2672                     # and resistant to trailing data.

  2673                     tr.addbackup(f, hardlink=True, location=b'plain')

  2674 

  2675             tr.addvalidator(b'dirstate-backup', backup_dirstate)