Patch to purge_experiments() to support removing repository_directory

[minghangli-uni]

This PR adds optional support for removing <test_path>/<repository_directory> when no <test_path>/<branch>/<repository_directory> directories exist under <test_path>.

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 96.60%. Comparing base (cababe7) to head (8ceb422).
⚠️ Report is 1 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff             @@
##             main      #27      +/-   ##
==========================================
+ Coverage   96.41%   96.60%   +0.18%     
==========================================
  Files           5        5              
  Lines         251      265      +14     
  Branches       40       44       +4     
==========================================
+ Hits          242      256      +14     
  Misses          3        3              
  Partials        6        6              

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