Global config cannot be set if ~/.gitconfig does not exist yet

When there is no ~/.gitconfig, the following code snippet

import pygit2
global_config = pygit2.Config.get_global_config() # ← Exception raised here
global_config['user.email'] = 'me@example.org'

fails with

Traceback (most recent call last):
  File "global_config.py", line 2, in <module>
    global_config = pygit2.Config.get_global_config()
  File "/usr/lib/python3/dist-packages/pygit2/config.py", line 281, in get_global_config
    return Config._from_found_config(C.git_config_find_global)
  File "/usr/lib/python3/dist-packages/pygit2/config.py", line 265, in _from_found_config
    check_error(err, True)
  File "/usr/lib/python3/dist-packages/pygit2/errors.py", line 53, in check_error
    raise IOError(message)
OSError: the global file '.gitconfig' doesn't exist: No such file or directory

I.e.,

1. there seems to be no way of setting a global option unless ~/.gitconfig already exists.
2. There seems to be no way to create the global config file ahead of time, at least not in a portable way (I doubt it is in ~/.gitconfig on Windows systems).

まず、~/.gitconfig がない状態で提供された Python スニペットを再現し、その後 pygit2/config.py、特に Config.get_global_config と _from_found_config を調べます。グローバル設定ファイルが存在しなくてもグローバルオプションを設定でき、かつその場所が異なるプラットフォームでも設定できれば、修正は完了です。