[Code-review] olpc-update patch

[C. Scott Ananian]

Dear code reviewers:

I recently had to make a more-major-than-usual change to olpc-update
to fix http://dev.laptop.org/ticket/7158

As described in the commit message:
http://dev.laptop.org/git?p=users/cscott/olpc-update;a=commitdiff;h=1ff49729ea98601cf2c983ab0031d1da9c302cf1

I changed the API used by the updater plugins for olpc-update so that
they no longer expect a (hardlinked) copy of the pristine tree to run
rsync on; instead they get an empty tree (or a tree filled with the
results of the last unsuccessful rsync attempt) and a lookaside
reference to the pristine tree which can be passed to rsync's
--link-dest option.

Since olpc-update is pretty important, I'd appreciate the extra eyes
to catch any thinkos I may have made in this refactoring.  Thanks.
 --scott

-- 
                         ( http://cscott.net/ )