WIP: write integration tests for update-scanning

scenarios:

• simple empty dir scan
• scan a single file
  • once
  • then add a tag, set a date, scan again
  • remove a tag, scan again
  • tag add+rm, scan again, go back to orig tags, scan again
  • delete file, scan again
  • "fast" scan scenario
    • perform an edit that doesn't change the size of the file
    • without waiting any time after the first scan. make sure the second scan picks up the edit.
• two files in root dir
  • scan both, once
  • create one, scan, add the other, scan
  • create both, scan, swap tags, scan, swap tags back, scan again (some tag overlap)
• dir/file.md
  • scan once
  • start with empty root, scan, then create them, and scan again
  • create, scan, add "adjacent" md file to the root dir, scan and check for note-unification (adding tags and date)
  • scan, then delete the dir, then scan again
• date paths
  • single file directly under date path - multiple scenarios
  • single directory under date path - make sure that note has date.
    • add adjacent file, make sure adjacent file date does not override path date
  • single files in several different dates
    • different year, different month, different day, and even same day.
    • make sure all note files are picked up.
    • make sure path date beats file date.
  • check that date dirs are also treated as notes.
• more complicated fs trees.... maybe multiple files and dirs changing?