core: Implement commands for operating on a single input line

This changes the commands delete_beginning_of_line, delete_end_of_line,
delete_line, move_beginning_of_line and move_end_of_line to operate on
the current line instead of the whole input. The commands
delete_beginning_of_input, delete_end_of_input, delete_input,
move_beginning_of_input and move_end_of_input are added with the
previous implementations that the line commands had.

Additionally, the commands move_previous_line and move_next_line are
added which moves the cursor to the previous/next line and keeps the
horizontal position in the line.

The meta-r key is changed from delete_line to delete_input to keep the
behavior, and because you probably want to delete the whole input more
often than the line. The meta-R key is added for delete_line.

The home, end, ctrl-u and ctrl-k keys are kept to the same commands,
which means that they change behaviour. This is because having them
operate on the line is consistent with other applications (vim, zsh),
and I also think it's more practical.

These new bindings are added:

    shift-home:  /input move_beginning_of_input
    shift-end:   /input move_end_of_input
    shift-up:    /input move_previous_line
    shift-down:  /input move_next_line
    meta-R:      /input delete_line
    meta-ctrl-u: /input delete_beginning_of_input
    meta-ctrl-k: /input delete_end_of_input

Relates to #1498

0 files changed, 0 insertions, 0 deletions