[Unison-hackers] Call for alpha-testers

[Benjamin Pierce]

All,

As you'll have noticed from the commit logs, Alan and I have been  
doing quite a bit of hacking the past week, trying to improve  
Unison's ability to deal with large files and directories.  This has  
required some major internal changes, which will take a little time  
to fully stabilize, but we *believe* that we've left all of Unison's  
paranoid double-checking mechanisms in place, so the new  
functionality should at least be fail-safe.  We'd love to have a few  
other people using it at this point, to help us shake out the last  
remaining bugs.

We've done two main things:

* Added support for resuming directory transfers if Unison is  
interrupted in the middle.  This functionality is always on, now.

* Added support for using an external utility for single-file  
transfers.  (Unison's built-in transport mechanism is not very fast  
for this case, so an external program like rsync can substantially  
improve performance.)  If the external program is able to resume  
interrupted transfers, this will make things even faster.

This functionality is enabled by setting the flag "copythreshhold" to  
something non-negative.  Setting it to zero will use the external  
program for all whole-file transfers (i.e., where the file has been  
created on one host).  Setting it to something positive will use the  
external program for transferring files larger than this value (in KB).

The external utility is rsync by default.  If you want to use a  
different one, set the "copyprog" and "copyprogrest" preferences.   
(They are documented in copy.ml.)

Please post a note here with any experiences, positive or negative.   
Thanks!

     - Benjamin

P.S.  Since things are changing fast, I have not packaged the new  
version as an explicit "release" -- better that alpha-testers just  
grab the current svn sources.