• #767: Add an "--ssh-command" flag to the "config bootstrap" action for setting a custom SSH
  command, as no configuration is available (including the "ssh_command" option) until
  bootstrapping completes.
• #794: Fix a traceback when the "repositories" option contains both strings and key/value pairs.
• #800: Add configured repository labels to the JSON output for all actions.
• #802: The "check --force" flag now runs checks even if "check" is in "skip_actions".
• #804: Validate the configured action names in the "skip_actions" option.
• #807: Stream SQLite databases directly to Borg instead of dumping to an intermediate file.
• When logging commands that borgmatic executes, log the environment variables that
  borgmatic sets for those commands. (But don't log their values, since they often contain
  passwords.)