from __future__ import absolute_import
from __future__ import print_function
from __future__ import unicode_literals

import subprocess


class CalledProcessError(RuntimeError):
    pass


def added_files():
    return set(cmd_output(
        'git', 'diff', '--staged', '--name-only', '--diff-filter=A',
    ).splitlines())


def cmd_output(*cmd, **kwargs):
    retcode = kwargs.pop('retcode', 0)
    popen_kwargs = {'stdout': subprocess.PIPE, 'stderr': subprocess.PIPE}
    popen_kwargs.update(kwargs)
    proc = subprocess.Popen(cmd, **popen_kwargs)
    stdout, stderr = proc.communicate()
    stdout = stdout.decode('UTF-8')
    if stderr is not None:
        stderr = stderr.decode('UTF-8')
    if retcode is not None and proc.returncode != retcode:
        raise CalledProcessError(cmd, retcode, proc.returncode, stdout, stderr)
    return stdout