pub fn ensure_owner_only_dir(dir: &Path) -> Result<OwnerOnlyOutcome>Expand description
Make dir owner-only on Unix: create it 0700 if missing (its parents
with the normal umask — they are the user’s, not AgentMux’s), or strip
group/other bits from an existing directory, keeping the owner bits as
they were. See DataPaths::ensure_dirs for why (#3682).
Follows a symlinked root to its target, as every other access to the root
already does. Errors if dir exists but is not a directory.