Also for dropping objects in direct mode.
Checking presence reliably needs a cache of mtime, size, and inode.
This way, if a file is modified, keys that point to it are no longer
present.
Also, the code for restoring the symlink when removing objects is
unnecessarily messy. calcGitLink was generating links starting with
"../../remote/.git/", when running "git annex move --from remote".
I put in a workaround, but calcGitLink should probably be fixed.
There is not yet support for getting objects from repositories in direct
mode; it still looks for content in .git/annex/objects, and there's no
once place I can change to fix that.
Also, getting objects from direct mode repositories is problematic since
the can be changed while the object is being transferred. It probably needs
to quarantine it first.
