Merge branch 'tb/clone-local-symlinks' into maint-2.30

Resolve a security vulnerability (CVE-2023-22490) where `clone_local()`
is used in conjunction with non-local transports, leading to arbitrary
path exfiltration.

* tb/clone-local-symlinks:
  dir-iterator: prevent top-level symlinks without FOLLOW_SYMLINKS
  clone: delay picking a transport until after get_repo_path()
  t5619: demonstrate clone_local() with ambiguous transport