Add basic support for emacs-like line editing.

[s10e-g]

Fix part of #152 by implementing some of the readline emacs mode line editing shortcuts on Linux local session and VT100 compatible terminal.

• [x] C-a move cursor to the beginning of the line
• [x] C-e move cursor to the end of the line
• [x] C-b move cursor backward
• [x] C-f move cursor forward
• [x] C-n get the next history
• [x] C-p get the previous history
• [x] C-t transpose chars
• [x] C-u unix line discard
• [x] C-k kill line
• [x] C-w unix word rubout
• [x] C-y yank (only one buffer. kill ring is not needed for now since M-y cannot be captured by read().)
• [x] C-l clear screen (only on VT100 compatible terminal)

TODO:

• [ ] C-r reverse search history
• [ ] Shortcuts with alt (cannot be captured by read())

[s10e-g]

Ultimately this function should be implemented using GNU readline or curses / unibilium. I fully understand that you want this library to remain independent of third-party libraries, but since C++ itself doesn't have any knowledge about the terminal, even a simple task like clear screen is not possible without reinventing ncurses.

Maybe it's ok to leave the user an option in the future?

[daniele77]

Thank you for your contribution. I'm against making the cli library dependent on other libraries. The library started with a strong dependency on boost, and I had much pressure to remove that dependency, and it cost me hard work. Now, I definitely do not want to add another dependency.