Re: garbage collection following a "git remote rm"?

"Robert P. J. Day" [off-list ref] writes:

  is there a command (git fsck?) that would display exclusively
objects in the object store corresponding to objects that are suddenly
unreferenced due to the removal of a remote?

fsck gives you dangling ones (and can be told to give you
unreachable ones, too) but the list will be more like "these are
unreachable, period".  It won't be like "these are the ones that
recently became unreacable, and I am not listing ones that were
unreachable already in N hours ago".