fn ensure_dir(dir: &Path, within: Option<&Path>) -> Result<()>Expand description
Creates the missing directories of dir, each 0700 at creation and
widened to 0755 once it exists, so the mode does not depend on the
umask (mkdir applies it to the requested mode: under 077 a 0755
request yields 0700, and scxcli list as a user could not read
/usr/share/scx). Directories that already exist are left as they
are, whatever their mode: those are the administrator’s.
With within (DESTDIR), the existing prefix is resolved before each
missing directory is made under it: pkg/usr/share -> /outside
would otherwise get an scx created in /outside before the file
itself is refused.