* Add specific key bindings to stage / unstage items
Feature requested by Issue #909.
* Updating Help popup with stage / unstage keys
* Merging staging and unstaging into a single `stage_unstage_item` key
* Add/remove hunk now use the `stage_unstage_item` key
Change `exit` (which exits the app regardless of context) to <kbd>Ctrl</kbd>+<kbd>C</kbd> (which doesn’t cause quitting on upper-case `Q` insert in popup inputs, cf. #771).
- Set default shortcut to `B` instead of `b` because the latter would
shadow `[b]ranches`.
- Add scrollbar.
- Show resolved commit id in title instead of `HEAD`.
- Make commit id bold if it is the commit id the file is blamed at.
- Don’t run blame on a binary file.
- Add shortcut for inspecting a commit in blame view.
