git hub config - refactor, rewrite, redux

[ingydotnet]

This issue is meant to address all the outstanding config related issues in a
complete and holistic way.

This closes the following issues:

• issue/213 (2016-02-13) open @perlpunk Allow to configure github hostname
• issue/91 (2016-02-13) open @dolmen Fallback to "git config github.user" for github.login
• issue/92 (2016-02-13) open @ingydotnet Allow git-hub config values to be per repo
• issue/93 (2016-02-13) open @ingydotnet Support a git-hub.default-remote for config
• pr/204 (2016-02-01) open @perlpunk add missing bash completion for config|config-unset
• pr/185 (2016-02-10) open @perlpunk add environment variable/config for force-cache

Design for this issue will follow in comments.

[ingydotnet]

The primary change is where git hub config will read from and write to.

The read order should be:

• $GIT_DIR/config if GIT_DIR exists
• $GIT_HUB_ROOT/config if GIT_HUB_ROOT exists
• ~/.git-hub/config
• ~/.gitconfig
• /etc/gitconfig

Where keys are read from a [git-hub] section.

The write order should be:

• $GIT_HUB_ROOT/config if GIT_HUB_ROOT exists
• ~/.git-hub/config

Any other behaviour can be accomplished with the git config command itself.

---

There will be a new doc section "Configuration" that explains all this. It
will be different from the git hub config command doc.

Config commands should hide auth tokens unless -T used.

Some keys can be taken from [github] sections if present.

[ewilhelm]

Seems like docs and code don't agree right now. Readme says ~/.git-hub/config and code only does ~/.githubconfig. nevermind, I must have gotten mixed up in updating (update: git-hub and git hub are different things for me despite having sourced the .rc file, I got /usr/lib/git-core/git-hub.)

Also, the .rc file sets GIT_HUB_ROOT, so I don't know about that as the default place to write unless this is made obvious by docs and setup/config output.

[perlpunk]

@ewilhelm where did you see code that still uses ~/.githubconfig ?