The nested flag must be set so that other autocommands can fire while
the BufReadCmd is still executing.

Checking if it's non-empty and not a directory gets us quite far, but
not all the way. While a working symlink would trigger the earlier
checks, a broken symlink does not.

This commit fixes the special case where ~/.local/share/nvim  already
exists but is a broken symlink. Thus, it fixes the following error on
startup:

E739: Cannot create directory /home/samuel/.local/share/nvim: file
already exists

tmux has a set-clipboard option which, when set to 'on', allows
applications to set the system clipboard using the usual OSC 52 escape
sequence.

Use the XTGETTCAP sequence to determine if the host terminal supports
the OSC 52 sequence and, if it does, enable the OSC 52 clipboard
provider by default.

This is only done automatically when all of the following are true:

  1. Nvim is running in the TUI
  2. 'clipboard' is not set to unnamed or unnamedplus
  3. g:clipboard is unset
  4. Nvim is running in an SSH connection ($SSH_TTY is set)
  5. Nvim is not running inside tmux ($TMUX is unset)

Problem:  matchparen highlight not cleared in completion mode
Solution: Clear matchparen highlighting in completion mode

Remove hard-coded hack in insexpand.c to clear the :3match before
displaying the completion menu.

Add a test for matchparen highlighting. While at it, move all test tests
related to the matchparen plugin into a separate test file.

closes: vim/vim#13493
closes: vim/vim#13524

https://github.com/vim/vim/commit/9588666360e94de3ff58d4bc79aa9148fbf5fc44

Co-authored-by: Christian Brabandt <cb@256bit.org>

matchparen: do not use hard-coded match id (vim/vim#13393)

* matchparen: do not use hard-coded match id

Instead of using the hard-coded match id 3, which may also be used by
other plugins, let the matchparen plugin use whatever ids are
automatically returned when calling matchaddpos().

For backwards-compatibility, keep the `:3match` call, which will still
use the hard-coded id 3 (as mentioned in :h :3match).

closes: vim/vim#13381

https://github.com/vim/vim/commit/d3e277f279ed628809eb6857ea3ebcfca566ca2a

Co-authored-by: Christian Brabandt <cb@256bit.org>