Add merge command to PyCharm again (including PEP8 corrections), see comments in https://www.jetbrains.com/pycharm/help/running-pycharm-as-a-diff-or-merge-command-line-tool.html

charm.diff

17,21c17,22
<     if arg == '-h' or arg == '-?' or arg == '--help':
<         print(('Usage:\n' + \
<                '  {0} -h |-? | --help\n' + \
<                '  {0} [-l|--line line] file[:line]\n' + \
<                '  {0} diff file1 file2').format(sys.argv[0]))
---
>     if arg in ['-h', '-?', '--help']:
>         print('Usage:\n'
>               '  {0} -h |-? | --help\n'
>               '  {0} [-l|--line line] file[:line]\n'
>               '  {0} diff file1 file2\n'
>               '  {0} merge local remote base merged'.format(sys.argv[0]))
23c24
<     elif arg == 'diff' and i == 0:
---
>     elif arg in ['diff', 'merge'] and i == 0:
25c26
<     elif arg == '-l' or arg == '--line':
---
>     elif arg in ['-l', '--line']:
35,37c36,38
<               args.append('-l')
<               args.append(line_number)
<               args.append(os.path.abspath(file_path))
---
>                 args.append('-l')
>                 args.append(line_number)
>                 args.append(os.path.abspath(file_path))
39c40
<               args.append(os.path.abspath(arg))
---
>                 args.append(os.path.abspath(arg))
42a44
> 
86c88,89
<         if launch_with_port(port): exit()
---
>         if launch_with_port(port):
>             exit()
88c91,92
<     if launch_with_port(port): exit()
---
>     if launch_with_port(port):
>         exit()