missing entries in "git help repository-layout"

  while writing up a cheat sheet with a visual layout of .git for my
students, i compared "git help repository-layout" to my git clone of
the kernel source tree, and noted the following things are not
mentioned in the repo layout help page -- i have no idea how complete
that page is supposed to be so it's entirely possible that these
omissions are deliberate:

  - ORIG_HEAD
  - FETCH_HEAD
  - description
  - gitk.cache
  - refs/
	bisect
	stash
  - logs/
	HEAD
	refs/
		stash
		remotes
  - worktrees/<id>/
	commondir
	HEAD
	index
	logs
	ORIG_HEAD

  as i said, i have no idea whether the entries above are deliberately
omitted from the layout page, i just made a list of them.

rday