• #609: Fix the glob expansion of "source_directories" values to respect the "working_directory"
  option.
• #609: BREAKING: Apply the "working_directory" option to all actions, not just "create". This
  includes repository paths, destination paths, mount points, etc.
• #562: Deprecate the "borgmatic_source_directory" option in favor of "user_runtime_directory"
  and "user_state_directory".
• #562: BREAKING: Move the default borgmatic streaming database dump and bootstrap metadata
  directory from ~/.borgmatic to /run/user/$UID/borgmatic, which is more XDG-compliant. You can
  override this location with the new "user_runtime_directory" option. Existing archives with
  database dumps at the old location are still restorable.
• #562, #638: Move the default check state directory from ~/.borgmatic to
  ~/.local/state/borgmatic. This is more XDG-compliant and also prevents these state files from
  getting backed up (unless you explicitly include them). You can override this location with the
  new "user_state_directory" option. After the first time you run the "check" action with borgmatic
  1.9.0, you can safely delete the ~/.borgmatic directory.
• #838: BREAKING: With Borg 1.4+, store database dumps and bootstrap metadata in a "/borgmatic"
  directory within a backup archive, so the path doesn't depend on the current user. This means
  that you can now backup as one user and restore or bootstrap as another user, among other use
  cases.
• #902: Add loading of encrypted systemd credentials. See the documentation for more information:
  https://torsion.org/borgmatic/docs/how-to/provide-your-passwords/#using-systemd-service-credentials
• #911: Add a "key change-passphrase" action to change the passphrase protecting a repository key.
• #914: Fix a confusing apparent hang when when the repository location changes, and instead
  show a helpful error message.
• #915: BREAKING: Rename repository actions like "rcreate" to more explicit names like
  "repo-create" for compatibility with recent changes in Borg 2.0.0b10.
• #918: BREAKING: When databases are configured, don't auto-enable the "one_file_system" option,
  as existing auto-excludes of special files should be sufficient to prevent Borg from hanging on
  them. But if this change causes problems for you, you can always enable "one_file_system"
  explicitly.
• #919: Clarify the command-line help for the "--config" flag.
• #919: Document a policy for versioning and breaking changes:
  https://torsion.org/borgmatic/docs/how-to/upgrade/#versioning-and-breaking-changes
• #921: BREAKING: Change soft failure command hooks to skip only the current repository rather than
  all repositories in the configuration file.
• #922: Replace setup.py (Python packaging metadata) with the more modern pyproject.toml.
• When using Borg 2, default the "archive_name_format" option to just "{hostname}", as Borg 2 does
  not require unique archive names; identical archive names form a common "series" that can be
  targeted together. See the Borg 2 documentation for more information:
  https://borgbackup.readthedocs.io/en/2.0.0b13/changes.html#borg-1-2-x-1-4-x-to-borg-2-0
• Add support for Borg 2's "rclone:" repository URLs, so you can backup to 70+ cloud storage
  services whether or not they support Borg explicitly.
• Add support for Borg 2's "sftp://" repository URLs.
• Update the "--match-archives" and "--archive" flags to support Borg 2 series names or archive
  hashes.
• Add a "--match-archives" flag to the "prune" action.
• Add "--local-path" and "--remote-path" flags to the "config bootstrap" action for setting the
  Borg executable paths used for bootstrapping.
• Add a "--user-runtime-directory" flag to the "config bootstrap" action for helping borgmatic
  locate the bootstrap metadata stored in an archive.
• Add a Zabbix monitoring hook. See the documentation for more information:
  https://torsion.org/borgmatic/docs/how-to/monitor-your-backups/#zabbix-hook
• Add a tarball of borgmatic's HTML documentation to the packages on the project page.