Problem:    ":write" fails after ":file name" and the ":edit".
Solution:   Reset BF_NOTEDITED when using ":edit". (closes vim/vim#10790)
https://github.com/vim/vim/commit/1f0dc5e84f5cc530c0fb9d0789e3d42d644429d7

vim-patch:8.2.1147: :confirm may happen in cooked mode

Problem:    :confirm may happen in cooked mode. (Jason Franklin)
Solution:   Switch to raw mode before prompting. (Brandon Pfeifer)
https://github.com/vim/vim/commit/27321dbeedf8bb833c48b01bf18536125794f65e

Code is N/A, but this improves tests. Port the improved tests to Lua.

Problem:    Insufficient testing for src/window.c.
Solution:   Add more tests. (Yegappan Lakshmanan, closes vim/vim#6345)
https://github.com/vim/vim/commit/5d3c9f8c2a0fc29ba4ac8e0f052378b64d9e3dd3

Cherry-pick test_tagjump.vim changes from patch 8.1.2373.

Problem:    Channel and sandbox code not sufficiently tested.
Solution:   Add more tests. (Yegappan Lakshmanan, closes vim/vim#5855)
https://github.com/vim/vim/commit/ca68ae13114619df3e4c195b41ad0575516f5ff6

Cherry-pick test_clientserver.vim changes form patch 8.2.0448.

Problem:    Various Normal mode commands not fully tested.
Solution:   Add more tests. (Yegappan Lakshmanan, closes vim/vim#5751)
https://github.com/vim/vim/commit/1671f4488105ee12a6a8558ae351436c26ab55fc

Cherry-pick a fix from patch 8.2.3162.
Omit test_iminsert.vim as previous patches to that file are N/A, and
Nvim doesn't support iminsert=2 either, so that test isn't useful.

Problem:    Various Ex commands not sufficiently tested.
Solution:   Add more test cases. (Yegappan Lakshmanan, closes vim/vim#5673)
https://github.com/vim/vim/commit/818fc9ad143911b2faa0d7cee86724aa70a02080

Needs to assert E170 instead of E580 because patch 8.2.3486 has been
ported but patch 8.2.1183 hasn't.

Problem:    Some code not covered by tests.
Solution:   Add test cases. (Yegappan Lakshmanan, closes vim/vim#5649)
https://github.com/vim/vim/commit/bc2b71d44a0b90b6aeb3534a76912fccbe5577df

Problem:    :helptags and some other functionality not tested.
Solution:   Add more tests. (Yegappan Lakshmanan, closes vim/vim#5567)
https://github.com/vim/vim/commit/e20b9ececa37a81c0340a78f61e57fa1bf46b06d

Problem:    Insufficient code coverage for ex_docmd.c functions.
Solution:   Add more tests. (Yegappan Lakshmanan, closes vim/vim#5618)
https://github.com/vim/vim/commit/9f6277bdde97b7767ded43a0b5a2023eb601b3b7

Cherry-pick Test_window_only() from patch 8.2.0203.
Cherry-pick a memory leak fix from patch 8.2.0399.

This can avoid divergences from Vim in some small places.