Re: reflog existence & reftable

> If there isn't, then we could do either one of these two things.
>
>  (1) we could add "git reflog create <ref>" and the reftable can
>      record the fact that "reflog exists for the ref, but no ref
>      movement recorded yet".  Then the condition C can be checked.
>
>  (2) we could declare that there is no way to create an empty reflog
>      supported across ref backends, and make the tests that rely on
>      the "feature" conditional on REF_FILES prerequisite.
>
> I have no strong preference.  In the early days I found the ability
> to limit which branches get logged convenient, so if reftable
> backend can learn the similar trick, we would want to go route (1)
> (the convenience largely came from the fact that there was no need
> to add one configuration item per branch, so I do not think we would
> want to bother with branch.<name>.reflog=bool configuration---that
> won't be an easy-to-use substitute).  On the other hand, logs are
> useful, and dormant logs are not costing anything (other than holding
> onto stale objects we may no longer want), so it could be that it
> may not be as convenient as it used to be to be able to turn logs on
> only on selected refs, in which case approach (2) is fine.