more git-annex plumbing

[Thomas Koch]

Hi,

I have a few things that I'd like to do with git-annex but that are hard 
because git-annex does not expose internal plumbing commands. I intend to 
start a list of such commands here with possible use cases:

- calculate checksum of a file
- doesAnnexHasChecksum?
- doesAnnexHasFile?

  Useful to deduplicate files from many old CD backups

- checksum to path
- move file into annex

  You already have an annexed file somewhere on the disk and just want to move 
it in the local annex without copying it

- find duplicates

  It might happen that a file is put into an annex in multiple places. One 
could try to find duplicate symlinks, but that's inefficient. As I understand, 
the git-annex data should allow a quick lookup of all symlinks pointing to a 
particular checkum.

I believe one reason why Git is so great is the available plumbing. 
Unfortunately I'm afraid I won't have time to learn any Haskell soon.

Thank you,

Thomas Koch, http://www.koch.ro