slackbuilds-current/development/quilt

These scripts allow to manage a series of patches by keeping track of the
changes each patch makes.  Patches can be applied, un-applied, refreshed, etc.

The key philosophical concept is that your primary output is patches - not ".c"
files, not ".h" files, but patches, so patches are the first-class object here.

Quilt was originally based on Andrew Morton's patch scripts published on the
linux kernel mailing list a while ago, but were heavily modified since then.