Consistent key bindings and control scheme

[alexmaco]

Rather than judging controls on a case-by-case basis, they should be made consistent across the application.
Secondly, controls should follow some patterns related to the action, and input mode (e.g. f should probably not be used for pull, since it's used for file finding in other places)

Third, there will be a lot of controls available for a lot of features. Simply listing all of them all the time in the command bar is most confusing to new users, i.e. people who need to read the command bar the most. While going through them myself it's sometimes not obvious what they do, why, and opening help means scrolling up and down, sometimes only to find a redundant description.

Obviously, changes here might result in breaking some backwards compatibility and some muscle memory, but I think consistency is worth it.

As a prototype for interaction, I suggest considering spacemacs as a starting model.
That is:

• having a few commands that work everywhere the same (search, arrow-based navigation, line selection, etc.), not all of which may need explicit marking everywhere
• having a few immediate commands 1 key combo away for the current view/mode (blame, push, pull, etc.)
• commands less often used can be treated either as options, or nested somewhere in modes i.e. 2 or 3 input steps until that action is reached (e.g. the --amend option for commit, or --fixup, or --interactive and/or --auto-squash for rebasing)
• interactive and searchable help that is part of the command bar to enable discovering what commands are available and how to invoke them (including ones in submenus/submodes). More extensive documentation and explanations should however still have its own mode/screen/popup.

The above may also imply some changes to how the command bar works.

Looking forward to other ideas and design considerations!