Seems to work, but still experimental until it's been tested more.
When repositories are on filesystems not supporting symlinks, the .git dir
symlink trick cannot be used. Since we're going to be in direct mode
anyway, the .git dir symlink is not strictly needed.
However, I have not fixed the code that creates new annex symlinks to
handle this case -- the committed symlinks will be wrong.
git annex sync happens to currently fail in a submodule using direct mode,
because there's no HEAD ref. That also needs to be dealt with to get
this fully working in crippled filesystems.
Leaving http://github.com/datalad/datalad/issues/44 open until these issues
are dealt with.
Avoids a warning message from git when HEAD doesn't exist. Which it won't
when eg, git-annex is used in a submodule just cloned with
git clone --recursive. In this case, a specific ref is checked out and
there's no HEAD yet.
The code already returned Nothing in this case, so no behavior change other
than not showing the warning. And git-annex operates fine in this
situation.
Most of the time, there will be no discreprancy between programPath and
readProgramFile.
But, the programFile might have been written by an old version of git-annex
that is still installed, while a newer one is currently running. In this
case, we want to run the same one that's currently running.
This is especially important for things like the GIT_SSH=git-annex used for
ssh connection caching.
The only code that still uses readProgramFile directly is the upgrade code,
which needs to know where the standalone git-annex was installed, in order to
upgrade it.
