--backup/--backup-dir filters feature req

[CaT]

Hi,

I was wondering if it would be possible to get filters purely for the
two backup flags. They would work in a similar manner to the current
ones except that they would only work on files to be backed up in order
to indicate what should be included in the backup and what should be
excluded.

This came up for me as part of daily server backups where I use
--backup-dir to have, effectively, daily diffs so that I can see what
files changed when and what they were in the past for an appropriately
long stretch back. The problem is that with one server I backup approx
100gb of data of which 70gb changes daily. I'm not interested in getting
diffs for that 70gb and so would like to exclude the files and dirs that
comprise them from the --backup file list, but I would like to keep
things like config file changes, etc in the daily diff.

At the moment I see two solutions, both of which are a tad messy.

1. Delete them after the rsync but this just wastes a whole lot of space
2. Do the rsync twice, but this can be real messy when the files are all
   over the place.

I do #1 at present but it means that I efectively lose 70gb of disk
space because I have to keep that buffer for the rsync to fully succeed.

Hope this made sense. :)

-- 
    "To the extent that we overreact, we proffer the terrorists the
    greatest tribute."
    	- High Court Judge Michael Kirby