Merge branch 'maint'

* maint:
  complete: zsh: use zsh completion for the main cmd
  complete: zsh: trivial simplification
  git-completion.bash: complete branch.*.rebase as boolean
  git-completion.bash: add diff.submodule to config list
  git-completion.bash: lexical sorting for diff.statGraphWidth

diff --cc contrib/completion/git-completion.bash
Simple merge