split_patch.py

#!/usr/bin/env python
#
# Takes a patch generated by format-patch as
# the first argument, and generates one patch file
# per diff inside that patch, to be applied with
# patch-am.  This helps you rebase on a file-by-file
# basis if you're so inclined.

import sys
import re

patch_file = file(sys.argv[1])
patch_lines = patch_file.readlines()

per_file_patches = []
per_file_filenames = []

diff_indexes = []

for i in xrange(len(patch_lines)):
  if patch_lines[i].startswith("diff "):
    diff_indexes.append(i)

assert len(diff_indexes) > 0

header = "".join(patch_lines[0:diff_indexes[0]])
for i in xrange(len(diff_indexes)):
  if i == len(diff_indexes) - 1:
    p = "".join(patch_lines[diff_indexes[i]:])
  else:
    p = "".join(patch_lines[diff_indexes[i]:diff_indexes[i+1]])
  file_guess = re.split("[ /]", patch_lines[diff_indexes[i]].rstrip())[-1]
  p = header + p
  p = re.sub("Subject: \[PATCH\]", "Subject: [PATCH] " + file_guess, p)
  per_file_patches.append(p)
  per_file_filenames.append(file_guess)

for i in xrange(len(per_file_patches)):
  f = file("%05d-%s.patch" % (i, per_file_filenames[i]), "w")
  f.write(per_file_patches[i])
  print f.name