The new oldtest directory is in test/old/testdir. The reason for this is
that many tests have hardcoded the parent directory name to be
'testdir'.

Problem:    It is not easy to use a script-local function for an option.
Solution:   recognize s: and <SID> at the start of the expression. (Yegappan
            Lakshmanan, closes vim/vim#9401)

https://github.com/vim/vim/commit/8bb65f230d3025037f34021a72616038da0601ee

Omit duplicate docs in fold.txt: removed in a later runtime update.
Cherry-pick test_diffmode.vim changes from patch 8.2.1432.

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

Problem:    Fix for recovery and diff mode not tested.
Solution:   Add a few more tests. (Yegappan Lakshmanan, closes vim/vim#8352)

https://github.com/vim/vim/commit/3044324e8dccd470bd854cf7d9457232cc9c220e

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

Problem:    Check for features implemented with "if".
Solution:   Use the Check commands. (Ken Takata, closes vim/vim#7383)

https://github.com/vim/vim/commit/aeb313f355cd67638e3c611354ce401d86f56afe

Cherry-pick test_compiler.vim changes from patch 8.1.2373.

Problem:    Not enough test coverage for evalvars.c.
Solution:   Add more tests. (Yegappan Lakshmanan, closes vim/vim#5804)

https://github.com/vim/vim/commit/8dfcce3a78ccb520cc9d09081f998091494c50bf

Assert E475 instead of E474 in :redir test because a later patch changed
the error number.

Comment out the test for :echo with a deeply nested container as Nvim
implements :echo very differently.

vim-patch:8.1.1915: more functions can be used as methods

Problem:    More functions can be used as methods.
Solution:   Make various functions usable as a method.
https://github.com/vim/vim/commit/1a3a89168d61c2fed91cbca812cf1c6983901b79

Move debugbreak() to the right place.

vim-patch:8.1.1921: more functions can be used as methods

Problem:    More functions can be used as methods.
Solution:   Make various functions usable as a method.
https://github.com/vim/vim/commit/a4208966fb289a505ebdef62bbc37c214069bab4

vim-patch:8.1.1953: more functions can be used as a method

Problem:    More functions can be used as a method.
Solution:   Allow more functions to be used as a method.
https://github.com/vim/vim/commit/f9f24ce7a0e5988fedf2e2ff751818f9b07510a6

Omit test_termcodes.vim: cannot be used and superseded by later patches.
Cherry-pick test_bufline.vim change from patch 8.1.1993.

Let :wincmd command accept a count like what its documentation suggests.
Previously it could only accept a range, which led to some ambiguity on
which attribute should be used when executing :wincmd using nvim_cmd.

Closes #19662.

Also fix a typo in a related Vim test:

vim-patch:9.0.0223: typo in diffmode test

Problem:    Typo in diffmode test.
Solution:   Fix the typo. (closes vim/vim#10932)
https://github.com/vim/vim/commit/5fd6ab820b4a0aaa5c6020852f39d118375fab49

Problem:    Invalid memory access in diff mode with "dp" and undo.
Solution:   Make sure the line number does not go below one.
https://github.com/vim/vim/commit/4e677b9c40ccbc5f090971b31dc2fe07bf05541d

Problem:    Test for DiffUpdated fails.
Solution:   Also accept a count of two.
https://github.com/vim/vim/commit/f65cc665fa751bad3ffe75f58ce1251d6695949f

Problem:    Invalid memory access after diff buffer manipulations.
Solution:   Use zero offset when change removes all lines in a diff block.
https://github.com/vim/vim/commit/c101abff4c6756db4f5e740fde289decb9452efa