Retrieve the relevant configuration for a repository

If either the global_config_path or system_config_path variables are not NULL, the given config files will be also included in the configuration set. The global configuration file is located in $HOME/.gitconfig. On most UNIX systems, the system config file file may be found on $sysconfdir/gitconfig.

The resulting git_config instance will query the files in the following order:

• Repository configuration file
  • Global configuration file
  • System configuration file

The method will fail if any of the given config files can't be found or accessed.

The returned git_config instance is owned by the caller and must be manually free'd once it's no longer on use.