Continued working on the enhancaed smudge/clean interface in git, incorporating feedback from the git developers.

In a spare half an hour, I made an improved-smudge-filters branch that teaches git-annex smudge to use the new interface.

Doing a quick benchmark, git checkout of a deleted 1 gb file took:

• 19 seconds before
• 11 seconds with the new interface
• 0.1 seconds with the new interface and annex.thin set
  (while also saving 1 gb of disk space!)

So, this new interface is very much worthwhile.