Like in issue #18089, this tar contains, same file name in two case
sensitive name version. Unpack should fail on case insensitive file
systems and succeed on case sensitive.

$ tar tvf 18089.tar
    18089/
    18089/alacritty/
    18089/alacritty/darkermatrix.yml
    18089/alacritty/Darkermatrix.yml