Re: `git-rev-parse master` not referred to by any ref?

"J. Bruce Fields" [off-list ref] writes:

quoted

Oops, found it:

	git$ cat .git/master
	407c0c87e15b3cf60347f4fc0bcdb4d239de4163

It _might_ make it safer to refuse creating anything outside
refs/ if the name does not contain or ends with "HEAD" (or
perhaps names that have chars outside "[_A-Z]"), but that would
restrict future tools that might want to have HEAD-like files,
so I am a bit hesitant.

OTOH, a random file under .git/ does not count as a ref for the
purposes of fsck/prune, so it may make sense to teach 
check_ref_format() about the same set of "special" names that
can appear directly under .git without being in refs/ hierarchy
(currently I think only "HEAD" and possibly "ORIG_HEAD" are in
that set).

BTW, git-merge.sh and git-reset.sh should use "git update-ref ORIG_HEAD"
instead of doing it by hand using "echo >$GIT_DIR/ORIG_HEAD".

Also, I *think* objects that are only reachable via ORIG_HEAD
are not considered as reachable by fsck/prune --- we probably
would want to fix this.