Simplify git-chain-rebases.
Add `locate` git alias.

This alias will grep through `git ls-files`.
Add the `origin-cherry` and `oc` git aliases.

These aliases run `git cherry` against the origin remote for the
specified branch or for the current branch.
Add the `cleanup` git alias.

This alias runs `git frune`, `git prune` and `git gc`.
Add the `filter.media` configuration options to gitconfig.
Show the SHA hash in the main tig window.
Set tig's tab size to 2.