Re: Shared repositories no longer securable against privilege escalation

Michael Haggerty [off-list ref] writes:

The locking was added intentionally, to ensure that the reflog for
`HEAD` is written safely. But the code didn't do that prior to the
commit that you referenced, so (as a special case) ignoring failures to
lock `HEAD` due to insufficient permission is probably a reasonable
compromise.

I think the special case could be restricted even further to when `HEAD`
has the `REF_LOG_ONLY` flag in the reference transaction. I don't think
that `HEAD` would ever show up in a transaction solely to verify its old
value in a typical server scenario, but if so, that situation could be
special cased too.

I find both of these acceptably good changes.