Presto: A project to add delta rpm support into yum for Fedora users
http://hosted.fedoraproject.org/projects/presto.  A list of presto-enabled
repositories is available there.

Installation:
=============
1- Install yum-presto on your system (yum -y install yum-presto)
2- Either use a repository that already has presto enabled in it or modify
   your .repo files so they contain the following:
     deltaurl = http://your-presto-repository.com
   where your-presto-repository.com is replaced with a valid presto repository
3- Now install an old rpm from a presto-enabled repository using rpm, then
   try updating it using yum. The plugin should kick in, try to download the
   drpm, reconstruct the full rpm, and yum should install that.

Notes:
======
Presto will read the deltaurl from two possible locations:
1. The repository's .repo file ("deltaurl = http://your-presto-repository.com")
2. Appended to /etc/yum/pluginconf.d/presto.conf in the form:
   [repository]
   deltaurl = http://your-presto-repository.com

Presto.conf has the following options in [main]:
keepdeltas=1               Always keep deltas in cache no matter what keepcache
                           is set to.
neverkeepdeltas=1          Always remove deltas after creating full rpms.
exitondownloadfailure=0|1  If there is a problem downloading the deltarpm, exit
                           rather than trying to download the full rpm.
Note: If you specify neither keepdeltas nor neverkeepdeltas, presto will follow
      the keepcache option in yum.conf.