Merge git://repo.or.cz/git-gui

Merge git://repo.or.cz/git-gui

* git://repo.or.cz/git-gui:
  git-gui: "Stage Line": Treat independent changes in adjacent lines better
  git-gui: Fix "Stage/Unstage Line" with one line of context.
  git-gui: Correct 'Visualize Branches' on Mac OS X to start gitk
  git-gui: Look for gitk in $PATH, not $LIBEXEC/git-core
  Add a menu item to invoke full copy detection in blame.
  Kill the blame back-end on window close.
  Add options to control the search for copies in blame.
  Fix pre-commit hooks under MinGW/MSYS