'git diff' against files outside a git repo

Hi all,

I'm interested in using 'git diff' on some files that aren't actually inside a git repo at all. Specifically, the --color-words and --word-diff-regex are really cool and I happen to have a use for them on files that aren't stored verbatim in git. As a whole, git's implementation of diff seems to be the fastest-moving one out there, so I'd rather use it instead of another random diff implementation.

(For the curious: the particular "files" I want to compare are actually split into a hierarchical tree of blobs using bup's rolling checksum and *then* stored in git. Obviously I have to reassemble them before I can diff them, which is fine and easy, but I then want to run 'git diff' against them, which seems to not be so easy.)

(For the extremely curious: the particular files I want to diff are mega-gigantic csv files from database dumps. Because of bup's tree format, I should be able to zoom in on just the overall part of the file that has changed, then diff only that, which will be much faster than running a diff algorithm against the whole file. Essentially O(log n) vs. the file size.)

Is there already a way to get 'git diff' to do this?

If not, would it be sensible to extend git-diff to do comparison between two outside files?

Or should I stop trying to do this and use some other diff implementation instead?

Another alternative would be to teach git directly how to act on bup-style large objects, but that's... a lot of work. And it's not obvious that a patch to do so would be accepted anyhow, since bup-style storage is necessarily not as space-efficient and is harder to deltify.

Thanks,

Avery