apache/spark — pull request #1668 by JoshRosen (2014-07-30 19:21:54+00:00)
Title: Improvements to merge_spark_pr.py

This commit fixes a couple of issues in the merge_spark_pr.py developer script:

- Allow recovery from failed cherry-picks.
- Fix detection of pull requests that have already been merged.

Both of these fixes are useful when backporting changes.