feature suggestion: no-backup filter modifier

[Matthew Monaco]

I think a modifier for filter rules that inhibits the --backup option
for the particular line might be useful.

for example I could have
--filter='H,nb /.mozilla/firefox/xxxxx.default/Cache'

or I could have

--filter'+ /Documents'
--filter'+,nb /.mozilla'

(So my documents will be backed up to --backup-dir but my firefox
profile will not)