Merge branch 'ar/mksnpath'

Merge branch 'ar/mksnpath'

* ar/mksnpath:
  Use git_pathdup instead of xstrdup(git_path(...))
  git_pathdup: returns xstrdup-ed copy of the formatted path
  Fix potentially dangerous use of git_path in ref.c
  Add git_snpath: a .git path formatting routine with output buffer
  Fix potentially dangerous uses of mkpath and git_path
  Fix potentially dangerous uses of mkpath and git_path
  Fix mkpath abuse in dwim_ref and dwim_log of sha1_name.c
  Add mksnpath which allows you to specify the output buffer

Conflicts:
	builtin-revert.c