Merge branch 'en/t3433-rebase-stat-dirty-failure'

The merge-recursive machinery failed to refresh the cache entry for a merge result in a couple of places, resulting in an unnecessary merge failure, which has been fixed. * en/t3433-rebase-stat-dirty-failure: merge-recursive: fix the refresh logic in update_file_flags t3433: new rebase testcase documenting a stat-dirty-like failure