Merge commit 'git-gui/master'

Merge commit 'git-gui/master'

* commit 'git-gui/master': (36 commits)
  git-gui: Change prior tree SHA-1 verification to use git_read
  git-gui: Include a space in Cygwin shortcut command lines
  git-gui: Use sh.exe in Cygwin shortcuts
  git-gui: Paper bag fix for Cygwin shortcut creation
  git-gui: Improve the Windows and Mac OS X shortcut creators
  git-gui: Teach console widget to use git_read
  git-gui: Perform our own magic shbang detection on Windows
  git-gui: Treat `git version` as `git --version`
  git-gui: Assume unfound commands are known by git wrapper
  git-gui: Correct gitk installation location
  git-gui: Always use absolute path to all git executables
  git-gui: Show a progress meter for checking out files
  git-gui: Change the main window progress bar to use status_bar
  git-gui: Extract blame viewer status bar into mega-widget
  git-gui: Allow double-click in checkout dialog to start checkout
  git-gui: Default selection to first matching ref
  git-gui: Unabbreviate commit SHA-1s prior to display
  git-gui: Refactor branch switch to support detached head
  git-gui: Refactor our ui_status_value update technique
  git-gui: Better handling of detached HEAD
  ...