patchutils

Patchutils is a small collection of programs that operate on patch files:

interdiff generates an incremental patch from two patches against a common source
combinediff generates a single patch from two incremental patches, allowing you to merge patches together
filterdiff will select the portions of a patch file that apply to files matching (or, alternatively, not matching) a shell wildcard
fixcvsdiff corrects the output of ‘cvs diff’
rediff corrects hand-edited patches, by comparing the original patch with the modified one and adjusting the offsets and counts
lsdiff displays a short listing of affected files in a patch file, along with (optionally) the line numbers of the start of each patch
splitdiff separates out patches from a patch file so that each new patch file only alters any given file once
grepdiff displays a list of the files modified by a patch where the patch contains a given regular expression
recountdiff fixes up counts and offsets in a unified diff
unwrapdiff fixes word-wrapped unified diffs.