• #542: Make the "source_directories" option optional. This is useful for "check"-only setups or
  using "patterns" exclusively.
• #574: Fix for potential data loss (data not getting backed up) when the "patterns" option was
  used with "source_directories" (or the "~/.borgmatic" path existed, which got injected into
  "source_directories" implicitly). The fix is for borgmatic to convert "source_directories" into
  patterns whenever "patterns" is used, working around a potential Borg bug:
  borgbackup/borg#6994