This is a todo for collecting changes that could lead to a v9 repository
version.

Currently, there does not seem to be enough reason to warrant one, but that
could change and if it does, these things could be included.

* Change locking of annexed files to use a separate lock file
  rather than posix locking the file itself.

  This would let write bits be removed from the file when
  core.sharedRepository is set. See <https://git-annex.branchable.com/bugs/shared_setting_of_git_causes_annex__39__ed_files_to_be_writeable__33__/>

  Note that windows already uses a separate lock file.

* Possibly enable `git-annex filter-process` by default. If the tradeoffs
  seem worth it.

  It does not currently incrementally hash, so implementing that first
  would imporve the tradeoffs.