v4 crashes on Windows if a subdirectory contains a dot file

[andreasabel]

error: invalid path 'test/aux/DuplicateExecutable/.gitignore'

Run actions/checkout@v4
...
Checking out the ref
  "C:\Program Files\Git\bin\git.exe" checkout --progress --force refs/remotes/pull/7719/merge
  Error: error: invalid path 'test/aux/DuplicateExecutable/.gitignore'
  Error: The process 'C:\Program Files\Git\bin\git.exe' failed with exit code 128

See https://github.com/agda/agda/actions/runs/13460302109/job/37613761843?pr=7719#step:2:54

[andreasabel]

Ah, actually no. aux seems to be an invalid name for a directory on Windows (my dim DOS knowledge comes back...).