Merge branch 'icasefs-symlink-confusion'

This topic branch fixes two vulnerabilities:

- Recursive clones on case-insensitive filesystems that support symbolic
  links are susceptible to case confusion that can be exploited to
  execute just-cloned code during the clone operation.

- Repositories can be configured to execute arbitrary code during local
  clones. To address this, the ownership checks introduced in v2.30.3
  are now extended to cover cloning local repositories.

Signed-off-by: Johannes Schindelin <johannes.schindelin@gmx.de>