PatchReader is a set of utilities for reading in, transforming, and doing
various other things with a patch.  It basically allows you to create a chain of
readers that can read a patch, remove files from a patch, add CVS context, fix
up the patch root according to CVS, and output the patch as raw unified or
through a template processor (used in some places to output a patch as HTML).

Homepage:
https://metacpan.org/release/PatchReader
