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:    Some tests fail on Cirrus CI and/or with FreeBSD.
Solution:   Make 'backupskip' empty. Do not run tests as root. Check for
            directory when using viminfo. (Ozaki Kiichi, closes vim/vim#6596)

https://github.com/vim/vim/commit/b86abadf87bd0f85f800077171ec4b98aefff776

Problem:    Not sufficient testing for buffer writing.
Solution:   Add a few tests. (Yegappan Lakshmanan, closes vim/vim#6238)

https://github.com/vim/vim/commit/1de5f7c81d5e78fb4d612134bd2dfa6ee9183fae

Problem:    Backup tests fail when CWD is in /tmp.
Solution:   Make 'backupskip' empty. (Christian Brabandt, closes vim/vim#3301)
https://github.com/vim/vim/commit/efe03738f69b1f63ea30226765db949539ee15f0

Problem:    Backup test fails when using shadow directory.
Solution:   Remove check for "src".
https://github.com/vim/vim/commit/f8f88f89e12df516c1fac5851b504238ebc1d2d4

Problem:    Using a full path is supported for 'directory' but not for
            'backupdir'. (Mikolaj Machowski)
Solution:   Support 'backupdir' as well. (Christian Brabandt, closes vim/vim#179)
https://github.com/vim/vim/commit/b782ba475a3f8f2b0be99dda164ba4545347f60f