Based on a patch by Matt, but further tweaked to deal with -q=foo.

Ultimately this should be upstreamed, but for now lets get this
functionality into rsync.

(Tweaked by Wayne to follow his preferred style.)

Rsync was showing the full destination path, which was confusing because
nothing is created at that path and was especially bogus in combination
with the source name of a solo file.

http://bugs.debian.org/cgi-bin/bugreport.cgi?bug=506830

because it is static.

It took me long enough to realize this that I think it is worth
documenting.

improve that of --inplace while I'm at it.

Originally explained at:

http://lists.samba.org/archive/rsync/2006-February/014838.html

- The receiver now sends keep-alive messages to the generator
  when it is actively doing work and hasn't sent anything
  recently.  This ensures that the generator won't timeout
  if the receiver is working hard.
- The perform_io() code has improved keep-alive participation.
- Allow the sender to send some keep-alive messages, which
  ensures that if it is in a lull, it can probe the socket.

the git-status checking into a library.

so that 3.0.7 knows we support the safer flist-xfer method.

The receiving side also switches timeout handling from the receiver to
the generator, which obviates the need for the sender to send any
keep-alive messages at all (for protocol 31 and beyond).  Given this
setup, all keep-alive messages are now sent as empty MSG_DATA messages,
with MSG_NOOP messages only being understood and (when necessary) acted
upon to forward a keep-alive event to an older receiver.  This is both
safer and more compatible with older versions.