Quick utility to create a backup of a branch.

git-posterity

#!/usr/bin/env python2.7
from __future__ import print_function, with_statement

import os
import sys
from subprocess import Popen, PIPE

def call(cmd_str, *more):
  args = cmd_str.split(' ')
  if more:
    args.extend(more)
  args = filter(None, args)
  print('>', ' '.join(args))
  p = Popen(args, stdout=PIPE, stderr=PIPE)
  out, err = p.communicate()
  return p.returncode, out, err

def call_or_die(*cmd):
  code, out, err = call(*cmd)
  if code != 0:
    sys.stderr.write(out)
    sys.stderr.write('\nError: {}'.format(err))
    sys.stderr.write('\n')
    sys.stderr.flush()
    sys.exit(1)
  return out.strip()

branch = call_or_die('git rev-parse --abbrev-ref HEAD')
branches = [s.strip().rsplit(' ', 1)[-1] for s in call_or_die('git branch').split('\n')]

def posterities(branch):
  i = 1
  while True:
    yield '{}-posterity{}'.format(branch, i if i > 1 else '')
    i += 1

for posterity in posterities(branch):
  if posterity not in branches:
    call_or_die('git checkout -b', posterity)
    call_or_die('git checkout', branch)
    break