but the cure appears to be worse than the disease.  It turns out that GNU
tar versions 1.14.x misinterpret -o as --same-owner, not --no-same-owner,
leading to exactly the wrong behavior for both root and nonroot users.
While that bug has been fixed for nearly five years, these tar versions
are still found in the wild, notably in OS X 10.4.  Given that #4883 was
the first complaint we'd heard, it's definitely not worth fixing at the
risk of breaking things for other users.  Perhaps revisit at a later date
when we're not up against a release deadline.