[Rev 01] RFR: Add pull request prune functionality

[Robin Westberg]

The pull request has been updated with additional changes.

----------------

Added commits:
 - 9983c27b: Improve test robustness

Changes:
  - all: https://git.openjdk.java.net/skara/pull/247/files
  - new: https://git.openjdk.java.net/skara/pull/247/files/83c41425..9983c27b

Webrevs:
 - full: https://webrevs.openjdk.java.net/skara/247/webrev.01
 - incr: https://webrevs.openjdk.java.net/skara/247/webrev.00-01

  Stats: 4 lines in 1 file changed: 3 ins; 0 del; 1 mod
  Patch: https://git.openjdk.java.net/skara/pull/247.diff
  Fetch: git fetch https://git.openjdk.java.net/skara pull/247/head:pull/247

PR: https://git.openjdk.java.net/skara/pull/247