[PATCH 0/2] Introduce ~/.gitconfig

These two patches introduce the long awaited global config. Thanks to Paksy for pushing and starting it.

The first patch only does the reading part, while the second introduces the --no-local flag to git-repo-config.

There are three subjects for discussion:

- The name. I personally prefer .gitconfig, since we talk about the repo
  config all the time. But I have no strong feelings there.

- The --no-local flag could be implemented more cleanly, but also less
  elegantly, by introducing git_config_set_multivar_in_file(). I hesitated
  to do that, because there would be even more places replicating the
  global / local path resolution.

- With this, repo-config does no longer merit its name. What do people think
  about making it a builtin named "git config"? (Of course, nothing hinders
  us to keep the synonymous "repo-config" indefinitely...)

Ciao, Dscho