The KDE sysadmins are well aware of that, at least. Mutable operations that would leave dangling blobs cause a backup copy of the appropriate ref to be generate

The KDE sysadmins are well aware of that, at least. Mutable operations that would leave dangling blobs cause a backup copy of the appropriate ref to be generated before the force-push/branch-deletion/etc. are run so that there's nothing for git to garbage collect.