Some of these handled multiline prompts but not multiline command lines. We
first need to move the cursor to the end of the commandline, then we can
print a message. Finally, we need to move the cursor back to where it was.
When we want to print something while the prompt is still active, we move the
cursor by printing a newline for each line in the prompt beyond the first
one. As established by 80fe0a7fc (fish_job_summary: Format message better
for multiline prompts, 2022-06-28), our use of "string repeat" actually
prints an extra newline. Let's remove it here as well.
We have some key bindings that print directly to the terminal while the user
is still typing the command line. Thereafter, we redraw the command line,
so the user can resume typing. To redraw a multiline command line, we first
erase several lines above the cursor. To not erase the key bindings' output,
we move the cursor down that many lines.
Simplify the logic; no functional change.
Corrects #6110
BSD `seq` produces a down-counting sequence when the second argument is
smaller than the first, e.g.:
$ seq 2 1
2
1
$
While GNU `seq` produces no output at all:
$ seq 2 1
$
To accommodate for this behavior, only run `seq` when we are sure that
the second argument is greater than or equal to the first (in this case,
the second argument `line_count` should be greater than 1).
* Fix default Alt+W keybinding
The old keybinding would chop off the last line of the `whatis` output
when using a multi-line prompt. This fix corrects that.
* Make variable local and remove unneeded if statement
* Test that token is non-empty
