Backup with mtree and rsync?

[schultz at ime.usp.br]

> I don't see any way to do this directly. What you probably want to do is
> use find(1) to pick out the new files to check, and then merge the
> changes into the old mtree(8) spec. Not trivial, but the spec syntax is
> intended to be easy to parse, so it shouldn't be that hard either.

What I am currently doing somewhat fits your description. I feed find
output into a C program that merges the old description with the
directory state to produce a new description. However, I use a format
different than mtree. I was seeking a shorter, more elegant, solution.

> It's possible that the mtree support in tar(8) might be able to do it,
> but it would probably be a lot slower.

Wait, can tar be used to remove files?