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

* git://git.kernel.org/pub/scm/gitk/gitk:
  gitk: Fix some bugs in the new cherry-picking code
  gitk: Improve responsiveness while reading and layout out the graph
  gitk: Update preceding/following tag info when creating a tag
  gitk: Add a menu item for cherry-picking commits
  gitk: Fix a couple of buglets in the branch head menu items
  gitk: Add a context menu for heads
  gitk: Add a row context-menu item for creating a new branch
  gitk: Recompute ancestor/descendent heads/tags when rereading refs
  gitk: Minor cleanups