Merge branch 'master' into next

* master:
  AsciiDoc fix for tutorial
  git.el: Added customize support for all parameters.
  git.el: Added support for Signed-off-by.
  git.el: Automatically update .gitignore status.
  git.el: Set default directory before running the status mode setup hooks.
  git.el: Portability fixes for XEmacs and Emacs CVS.
  contrib/emacs: Add an Emacs VC backend.