Not implemented Instead of listing explicitly, prune all refs.

Not implemented Entries older than this time are pruned. Without the option it is taken from configuration `gc.reflogExpire`, which in turn defaults to 90 days.

Not implemented Entries older than this time and not reachable from the current tip of the branch are pruned. Without the option it is taken from configuration `gc.reflogExpireUnreachable`, which in turn defaults to 30 days.

Not implemented While expiring or deleting, adjust each reflog entry to ensure that the `old` sha1 field points to the `new` sha1 field of the previous entry.

Not implemented This revamps the logic -- the definition of "broken commit" becomes: a commit that is not reachable from any of the refs and there is a missing object among the commit, tree, or blob objects reachable from it that is not reachable from any of the refs. + This computation involves traversing all the reachable objects, i.e. it has the same cost as 'git-prune'. Fortunately, once this is run, we should not have to ever worry about missing objects, because the current prune and pack-objects know about reflogs and protect objects referred by them.

Not implemented Update the ref with the sha1 of the top reflog entry (i.e. @\{0\}) after expiring or deleting.

Not implemented Print extra information on screen.