Merge branch 'tz/completion'

The completion helper code now pays attention to repository-local
configuration (when available), which allows --list-cmds to honour
a repository specific setting of completion.commands, for example.

* tz/completion:
  completion: use __git when calling --list-cmds
  completion: fix multiple command removals
  t9902: test multiple removals via completion.commands
  git: read local config in --list-cmds