I need a diff (or patch) manipulation utility, but unfortunately I have not found one, then I wrote one, of course, it's in Python.

#!/usr/bin/python

import sys, os

# Usage: diff-filter [-v] path1 path2 ...
#                    <INPUT >OUTPUT
if len(sys.argv) <= 1:

    print "Usage: %s [-v] path1 path2 ... <INPUT" % \
            os.path.basename(sys.argv[0])

    sys.exit(1)

# some global variables
inChunk = True

strip   = 1
matched = False
buffer  = ''

invert  = False

# to invert the filter
if sys.argv[1] == '-v':

    invert = True
    del sys.argv[1]

# the main filter
while True:
    line = sys.stdin.readline()

    if not line:
        break

    if line.startswith("--- ") or \
            line.startswith("diff") or \
            line.startswith("Binary") or \
            line.startswith("Index"):

        matched = False
        inChunk = False

        if line.startswith("diff") or \
            line.startswith("Binary") or \
            line.startswith("Index"):

            buffer += line
            continue
        else:
            path = line.split()[1]

            slash = path.find('/')
            path = path[slash+1:]

            for arg in sys.argv[1:]:
                if path.startswith(arg):

                    matched = True
                    break
            else:
                matched = False

        if invert:
            matched = not matched
        if not matched:

            buffer = ''

    if inChunk:
        print line,

    if matched:
        if buffer:
            print buffer,

            buffer = ''
        print line,

It also can be reached by the ubuntu paste service:

http://paste.ubuntu.com/166435/

Application field: if you have a big diff generated by "diff -R", and want to split it according to some seperate path or components, you can use this. Happy hacking!