particular, it will keep not only objects referenced by your current set
of branches and tags, but also objects referenced by the index, remote
tracking branches, refs saved by 'git-filter-branch' in
-refs/original/, or reflogs (which may references commits in branches
+refs/original/, or reflogs (which may reference commits in branches
that were later amended or rewound).
If you are expecting some objects to be collected and they aren't, check