Problem:    :registers command does not work in sandbox.
Solution:   Add flag to the command. (closes vim/vim#12473)

https://github.com/vim/vim/commit/eb43b7f0531bd13d15580b5c262a25d6a52a0823

Co-authored-by: Julio B <julio.bacel@gmail.com>

Problem:    Cleaning up afterwards can make a function messy.
Solution:   Add the :defer command.

https://github.com/vim/vim/commit/1d84f7608f1e41dad03b8cc7925895437775f7c0

Omit EX_EXPR_ARG: Vim9 script only.
Make :def throw E319 to avoid confusing behavior.

Co-authored-by: Bram Moolenaar <Bram@vim.org>

vim-patch:8.2.0695: Vim9: cannot define a function inside a function

Problem:    Vim9: cannot define a function inside a function.
Solution:   Initial support for :def inside :def.

https://github.com/vim/vim/commit/04b12697838b232b8b17c553ccc74cf1f1bdb81c

vim-patch:8.2.0725: Vim9: cannot call a function declared later in Vim9 script

Problem:    Vim9: cannot call a function declared later in Vim9 script.
Solution:   Make two passes through the script file.

https://github.com/vim/vim/commit/09689a02840be40fa7bb10b1921fb5bc5b2908f1

vim-patch:8.2.0734: Vim9: leaking memory when using :finish

Problem:    Vim9: leaking memory when using :finish.
Solution:   Do not check for next line in third pass.

https://github.com/vim/vim/commit/04816717dfea6e2469ff4c9d40f68b59aaf03724

vim-patch:8.2.0753: Vim9: expressions are evaluated in the discovery phase

Problem:    Vim9: expressions are evaluated in the discovery phase.
Solution:   Bail out if an expression is not a constant.  Require a type for
            declared constants.

https://github.com/vim/vim/commit/32e351179eacfc84f64cd5029e221582d400bb38

vim-patch:8.2.0818: Vim9: using a discovery phase doesn't work well

Problem:    Vim9: using a discovery phase doesn't work well.
Solution:   Remove the discovery phase, instead compile a function only when
            it is used.  Add :defcompile to compile def functions earlier.

https://github.com/vim/vim/commit/822ba24743af9ee1b5e7f656a7a61a38f3638bca

vim-patch:8.2.0819: compiler warning for unused variable

Problem:    Compiler warning for unused variable.
Solution:   Remove the variable.

https://github.com/vim/vim/commit/f40e51a880a95f94dbbbecc9476559506c2cc345

vim-patch:8.2.0822: Vim9: code left over from discovery phase

Problem:    Vim9: code left over from discovery phase.
Solution:   Remove the dead code.

https://github.com/vim/vim/commit/2eec37926db6d31beb36f162ac00357a30c093c8

Co-authored-by: Bram Moolenaar <Bram@vim.org>

just use the individual options instead.

   set selection=exclusive
   set selectmode=mouse,key
   set mousemodel=popup
   set keymodel=startsel,stopsel

existing behavior of
  :=
and
  :[range]=

are unchanged. `|` is still allowed with this usage.

However,
   :=p
and similar are changed in a way which could be construed as a breaking
change. Allowing |ex-flags| for := in the first place was a mistake as
any form of := DOES NOT MOVE THE CURSOR. So it would print one line number
and then print a completely different line contents after that.

Problem:    No completion for :scriptnames.
Solution:   Implement :scriptnames completion. (Yegappan Lakshmanan,
            closes vim/vim#10005)

https://github.com/vim/vim/commit/454ce6737cadb82886f1fc0eb9e8666cc59ae42b

Co-authored-by: Yegappan Lakshmanan <yegappan@yahoo.com>

Co-authored-by: Justin M. Keyes <justinkz@gmail.com>