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
assert.True(t,equal,"Unexpected change in the diff string: expected hash: %s but was actually: %s",diffHash,actual)
assert.True(t,equal,"Unexpected change in the diff string: expected hash: %s size: %d but was actually: %s size: %d",hex.EncodeToString([]byte(diffHash)),diffLength,hex.EncodeToString([]byte(actual)),actualLength)
// We need to save all of the data used to compute this merge as it may have already been changed by TestPatch. FIXME: need to set some state to prevent TestPatch from running whilst we are merging.