Quilt is a set of scripts that allows 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.