Commit 5f849d0 changed control-C to print an inverted ^C and then a newline.
The original motivation was
> In bash if you type something and press ctrl-c then the content of the line
> is preserved and the cursor is moved to a new line. In fish the ctrl-c just
> clears the line. For me the behaviour of bash is a bit better, because it
> allows me to type something then press ctrl-c and I have the typed string
> in the log for further reference.
This sounds like a valid use case in some scenarios but I think that most
abandoned commands are noise. After all, the user erased them. Also, now that
we have undo that can be used to get back a limited set of canceled commands.
I believe the original motivation for existing behavior (in other shells) was
that TERM=dumb does not support erasing characters. Similarly, other shells
like to leave behind other artifacts, for example when using tab-completion
or in their interactive menus but we generally don't.
Control-C is the obvious way to quickly clear a multi-line commandline.
IPython does the same. For the other behavior we have Alt-# although that's
probably not very well-known.
Restore the old Control-C behavior of simply clearing the command line.
Our unused __fish_cancel_commandline still prints the ^C. For folks who
have explicitly bound ^C to that, it's probably better to keep the existing
behavior, so let's leave this one.
Previous attempt at #4713 fizzled.
Closes#10213
