inhibit: ensure that no obsolete changesets are visible after a bookmark change
When creating a bookmark, we could reveal obsolete changesets. We are
inhibiting the obsolete changesets resulting from a bookmark change.
There are two ways to record bookmark changes to disk and we wrap both.
inhibit: ensure no visible changesets are obsolete after an update
When updating to a commit we want to inhibit any obsolete commit affecting
the changeset we are updating to. In other words we don't want any
visible commit to be obsolete.