Merge git://git.kernel.org/pub/scm/gitk/gitk

* git://git.kernel.org/pub/scm/gitk/gitk:
  gitk: Better workaround for arrows on diagonal line segments
  gitk: Allow top panes to scroll horizontally with mouse button 2
  gitk: Prevent parent link from overwriting commit headline
  gitk: Show diffs for boundary commits
  gitk: Use the new --boundary flag to git-rev-list