Merge branch 'master' into next

* master:
  t0003: properly quote $HOME
  contrib/ciabot: git-describe commit instead of HEAD
  Fix a formatting error in git-merge.txt
  git-gui: apply color information from git diff output
  git-gui: use wordprocessor tab style to ensure tabs work as expected
  git-gui: correct assignment of work-tree
  git-gui: use full dialog width for old name when renaming branch
  git-gui: generic version trimming
  git-gui: enable the Tk console when tracing/debugging on Windows
  git-gui: show command-line errors in a messagebox on Windows
  On Windows, avoid git-gui to call Cygwin's nice utility