Keyboard shortcuts:
ata²-specific:
Ctrl-D, EOF         (In multiline mode) Send the current message.
F2                  Save the current conversation (not including the message
                    you're typing) to a file.

rustyline:
Ctrl-A, Home        Move cursor to the beginning of line
Ctrl-B, Left        Move cursor one character left
Ctrl-E, End         Move cursor to end of line
Ctrl-F, Right       Move cursor one character right
Ctrl-H, Backspace   Delete character before cursor
Ctrl-I, Tab         Next completion
Ctrl-K              Delete from cursor to end of line
Ctrl-L              Clear screen
Ctrl-N, Down        Next match from history
Ctrl-P, Up          Previous match from history
Ctrl-X Ctrl-U       Undo
Ctrl-Y              Paste from Yank buffer (Meta-Y to paste next yank instead)
Meta-<              Move to first entry in history
Meta->              Move to last entry in history
Meta-B, Alt-Left    Move cursor to previous word
Meta-C              Capitalize the current word
Meta-D              Delete forwards one word
Meta-F, Alt-Right   Move cursor to next word
Meta-L              Lower-case the next word
Meta-T              Transpose words
Meta-U              Upper-case the next word
Meta-Y              See Ctrl-Y
Meta-Backspace      Kill from the start of the current word, or, if between
                    words, to the start of the previous word
Meta-0, 1, ..., -   Specify the digit to the argument. – starts a negative
                    argument.

Thanks to <https://github.com/kkawakam/rustyline#emacs-mode-default-mode>.
