1fe5fe419e
Backport #15352 The issue is that the TestPatch will reset the PR MergeBase - and it is possible for TestPatch to update the MergeBase whilst a merge is ongoing. The ensuing merge will then complete but it doesn't re-set the MergeBase it used to merge the PR. Fixes the intermittent error in git test. Signed-off-by: Andrew Thornton art27@cantab.net