p4-diff-changelist.py

#!/usr/bin/env python3
#
# Copyright 2014-2020 Cameron Hart <cameron.hart@gmail.com>.
# All rights reserved.
#
# Redistribution and use in source and binary forms, with or without
# modification, are permitted provided that the following conditions are met:
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#    1. Redistributions of source code must retain the above copyright notice,
#       this list of conditions and the following disclaimer.
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#    2. Redistributions in binary form must reproduce the above copyright
#       notice, this list of conditions and the following disclaimer in the
#       documentation and/or other materials provided with the distribution.
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# THIS SOFTWARE IS PROVIDED BY COPYRIGHT HOLDER ``AS IS'' AND ANY EXPRESS OR
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# ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
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# GistID: 9337378
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import argparse
import re
import subprocess

def stripPath(path, count):
  try:
    return '/'.join(path.split('/')[count:])
  except IndexError:
    return path

# Converts p4 describe's unified diff format into GNU unified diff format.
# https://www.gnu.org/software/diffutils/manual/html_node/Detailed-Unified.html

def diff(changelist, stripDepth=0):
  command = ('p4 describe -S -du %d' % changelist).split()

  proc = subprocess.Popen(command, stdout = subprocess.PIPE)
  output = proc.communicate()[0]

  header = re.compile('==== /([^#]+)#\d+ [^ ]+ ====')
  for bline in output.splitlines(False):
    line = bline.decode('utf-8')
    m = header.match(line)
    if m:
      pathA = stripPath('/a%s' % m.group(1), stripDepth)
      pathB = stripPath('/b%s' % m.group(1), stripDepth)

      # print GNU unified diff compliant header
      print('--- %s' % pathA)
      print('+++ %s' % pathB)
    else:
      print(line)

def main():
  parser = argparse.ArgumentParser(description=
      'Converts p4 describe unified diff format into GNU unified diff format')
  parser.add_argument('changelist', type=int, help='p4 changelist number')
  parser.add_argument('-p', '--strip', dest='stripDepth', type=int, help='Same as GNU patch -pN, pre-strip paths to the given depth.')
  args = parser.parse_args()
  diff(args.changelist, args.stripDepth)

if __name__ == '__main__':
  main()