- ref #14083 #15251
- also: docs: naming conventions

Analogous to nodejs's `on('data', …)` interface, here on_key is the "add
listener" interface.

ref 3ccdbc570d85 #12536

BREAKING_CHANGE: vim.register_keystroke_callback() is now an error.

Some programs behave differently when they detect that stdin is being
piped. This can be problematic when these programs are used with the job
control API where stdin is attached, but not typically used. It is
possible to run the job using a PTY which circumvents this problem, but
that includes a lot of overhead when simply closing the stdin pipe would
suffice.

To enable this behavior, add a new parameter to the jobstart options
dict called "stdin" with two valid values: "pipe" (the default)
implements the existing behavior of opening a channel for stdin and
"null" which disconnects stdin (or, if you prefer, connects it to
/dev/null). This is extensible so that other modes can be added in the
future.

Ensure that
  * Shell uses UTF8 input/output mode
  * Stderr output is captured, in UTF8
  * Program exit codes are correctly captured

Update functional test harness and add tests
for :make command.

Closes #13713

PR #13998 added support for floating window borders.

too old now, can be confusing

* Add buffer information to tabline_update

Most terminal implementations of the tabline display buffer and tab
information. Many neovim-qt users disable GuiTabline because it lacks
functionality provided in the terminal implementation.

The tabline_update event should include buffer information too, so client GUIs
can display rich useful tabs.

v8.2.0886 isn't ported yet.
Also remove mentions of Vim9 and legacy script for now.

[skip ci]

Closes #14386