handy text editor

An experimental text editor. This code is unstable, untested, used
only for experimentation by David Capello.

Concepts

Doc: a open document, associated to a file in disk when the document is loaded from a file/saved to a file.
View: a view to visualize a document (DocView), a browsing a file (DirView), etc.
Mode: a view can be in one of the following modes:
- Mode::Nav: Navigating document/view.
- Mode::Ins: Inserting/editing text in the document.
- Mode::Cmd: Calling a command by hand (entering command name).
- Mode::Sel: Selecting text.
- Mode::Sea: Searching text.

Some random notes about the “handy” UX:

Start on editing mode (DocView+Ins mode) when the program is launched with a file name as argument.
Start on with a file browsing interface (DirView) showing the current directory when the program is started without arguments.
From this view it should be easy to create new files in the directory or navigate to other directories, open files, etc.
Editing mode by default with access to special modes with Ctrl+common shortcut (like Ctrl+F to find text in the document).
Git views: status, log, commit, and diff views.
Zip views: list files inside, view files, extract files (re-compress?).
General shortcuts guidelines:
- Similar layout to handy-mode + modes
- Ctrl+Q: closes the program (ask for saving changes)
- Nav: J/I/L/K=previous char/line and next char/line, Enter/Space/Backspace=enter to Ins mode
- Ins: Esc=go back to Nav mode
- Sel: Enter=finish selection
- Sea: Ctrl+F=go to next result, Enter=exit Sea mode

This program is being developed on macOS. There are no short-term
plans to port it to other platforms yet.

handy depends on the following open source projects: