I've been investigating ways to implement a [[/todo/direct_mode_guard]].
Preventing a stray `git commit -a` or `git add` doing bad things in a
direct mode repository seems increasingly important.

First, considered moving `.git`, so git won't know it's a git repository.
This doesn't seem *too* hard to do, but there will certianly be unexpected
places that assume `.git` is the directory name.

I dislike it more and more as I think about it though, because it moves
direct mode git-annex toward being entirely separate from git, and I don't
want to write my own version control system. Nor do I want to complicate
the git ecosystem with tools needing to know about git-annex to work in
such a repository.

So, I'm happy that one of the other ideas I tried today seems quite
promising. Just set core.bare=true in a direct mode repository. This nicely
blocks all git commands that operate on the working tree from doing
anything, which is just what's needed in direct mode, since they don't know
how to handle the direct mode files. But it lets all git commands and other
tools that don't touch the working tree continue to be used. You can even
run `git log file` in such a repository (surprisingly!)

It also gives an easy out for anyone who really wants to use git commands
that operate on the work tree of their direct mode repository, by just
passing `-c core.bare=false`. And it's really easy to implement in
git-annex too -- it can just notice if a repo has core.bare and
annex.direct both set, and pass that parameter to every git command it
runs. I should be able to get by with only modifying 2 functions to
implement this.
