I've noticed a patch 8.2.4376 that uses more Xtest directories.
Change $TMPDIR to X-test-tmpdir to avoid more future divergence.

vim-patch:8.2.3564: invalid memory access when scrolling without valid screen

Problem:    Invalid memory access when scrolling without a valid screen.
Solution:   Do not set VALID_BOTLINE in w_valid.

https://github.com/vim/vim/commit/777e7c21b7627be80961848ac560cb0a9978ff43

Remove -Z flag when using RunVim().

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

Problem:    Exit test causes spurious valgrind reports.
Solution:   Skip test.  Add CheckNotValgrind.

https://github.com/vim/vim/commit/cf801d4b95180ddaee1bf633ef482232625dd80b

Cherry-pick RunningWithValgrind() from patch 8.2.5136.

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

Problem:    Test 49 is old style.
Solution:   Convert test cases to new style. (Yegappan Lakshmanan,
            closes vim/vim#6638)

https://github.com/vim/vim/commit/9470a4d88acf948af1596101527b3a505f8c14e9

Cherry-pick AssertException() from patch 8.2.1146.

Problem:    Some tests fail when run as root.
Solution:   Add CheckNotRoot and use it. (James McCoy, closes vim/vim#5020)
https://github.com/vim/vim/commit/07282f01da06c158bab4787adc89ec15d7eeb202

Skip test_terminal.vim and test_viminfo.vim: N/A

Prep for patch v8.2.0511.

Problem:    Various comments can be improved.
Solution:   Various comment adjustments.
https://github.com/vim/vim/commit/22286895fce0e45e42126c7f2e35ebf43bc625d9

Problem:    Screenshot tests may use a different encoding. (Dominique Pelle)
Solution:   Always set 'encoding' to "utf-8" when running Vim in a terminal.
            (closes vim/vim#4884)
https://github.com/vim/vim/commit/0fdddeeb66bbe326860ddfc573eba42f6487bbda

Comment out the encoding change in shared.vim
because Neovim always uses utf-8 for internal character encoding.

Problem:    Netbeans test sometimes fails.
Solution:   Mark any test using an external command as flaky.
https://github.com/vim/vim/commit/4a070cc82e00618db279526797564cb2b4e9b060

Problem:    When testing in the GUI may try to run gvim in a terminal.
Solution:   Add the -v argument. (Yee Cheng Chin, closes vim/vim#4605)  Don't skip
            tests that work now.
https://github.com/vim/vim/commit/0d702028feb859e6bde9a0c943d398d86294beb7