Config reader does not support includeIf #1053

If the .gitconfig file includes an includeIf directive, the config parser doesn't respect it.

~/.gitconfig file contents:

[includeIf "gitdir:~/work/git/"]
        path = ~/.gitconfig.work

[user]
        email = my@email.com
        name = Me
        useconfigonly = true

~/.gitconfig.work contents

[user]
        email: work@email.com
        name = Work

Change to the ~/work/git/project directory and run git config -l and notice that the name is set to Work. Running the following in a Python REPL

import os
from git import Repo
repo = Repo(os.getcwd())
repo.repo.config_reader().get_value("user", "name")
'Me'

And if the user hasn't got a default user setting in the ~/gitconfig file, it will throw ConfigParser.NoSectionError: No section: 'user' which is expected.

Config parser should support the includeIf directive in the config file.