plain source -> encrypted destination: rsync + gpg

[Kyle Jones]

addady at active.co.il writes:
 > > If i recall correctly (i've not gone back to review that
 > > patch) that patch required whole-file transfers two avoid
 > > doing the operation twice per file.  If the filter is
 > > deterministic and particularly if changes have minimal
 > > cascade effect you may be able to still take advantage of
 > > the rsync algorithm.
 > 
 > You recall correctly.
 > It is not clear to me how using "whole-file" and still take advantage of
 > the rsync algorithm.

Right.  I was willing to give up the checksumming for my
application.  It seems that you could code a --source-filter
patch that would

- compare the source and destination modtimes
- if they differ, then apply the filter to the source file storing
  the output in a temp file.  compare the temp file checksums
  against the remote file checksums and transmit the parts that
  have changed.

This would be better than my --dest-filter patch.