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:    assert_fails() checks the last error message.
Solution:   Check the first error, it is more relevant.  Fix all the tests
            that rely on the old behavior.

https://github.com/vim/vim/commit/9b7bf9e98f06ece595fed7a3ff53ecce89797a53

Skip test_listener.vim, test_textprop.vim, test_viminfo.vim.
Skip test_python2.vim: affected line fails and hasn't been ported.
Skip test_python3.vim: affected lines fail and haven't been ported.
Skip CHECK_LIST_MATERIALIZE.

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

Problem:    Window-local directory is not applied if 'acd' fails.
Solution:   Don't call do_autochdir(). (closes vim/vim#9891)
https://github.com/vim/vim/commit/b29ae159777028bb3266835b55716749ab0515be

Problem:    Restoring directory after using another window is inefficient.
Solution:   Only restore the directory for win_execute().  Apply 'autochdir'
            only when needed.
https://github.com/vim/vim/commit/90c317f2246a7fb4bd4e3feb0778b53627bc9fad

Problem:    Autochdir test fails without the +channel feature.
Solution:   Remove the ch_logfile() call. (Dominique Pellé, closes vim/vim#9281)
https://github.com/vim/vim/commit/f661cee847d2c17652b0ad0d703d2e3ac8610265

Problem:    In wrong directory when using win_execute() with 'acd' set.
Solution:   Restore the directory when returning to the window. (closes vim/vim#9276)
https://github.com/vim/vim/commit/dea4a616376c6500894c16e26057ce16d7ef9f0e

Problem:    Autochdir test fails on MS-Windows.
Solution:   Expecta nother error on MS-Windows.
https://github.com/vim/vim/commit/adbb383e0f2bb59286ea8133f02c448fd334958f

Problem:    Crash when using special multi-byte character.
Solution:   Don't use isalpha() for an arbitrary character.
https://github.com/vim/vim/commit/5921aeb5741fc6e84c870d68c7c35b93ad0c9f87

Rename vim_isalpha to mb_isalpha.

Problem:    "verbose pwd" shows confusing info when :lcd does not change
            directory.
Solution:   Clear last_chdir_reason also when the directory does not change.
            (closes vim/vim#9160)
https://github.com/vim/vim/commit/64be6aa3a54ecfe355d4a03e1200650c301e7f29

This only ports the tests, as this is already Nvim's behavior.

Problem:    ":verbose pwd" does not mention 'autochdir' was applied.
Solution:   Remember the last chdir was done by 'autochdir'.  (issue vim/vim#9142)
https://github.com/vim/vim/commit/0526815c15170a5926e1008600ec29d42d8b64c2