* Means a minimum of 2x as much time spent resolving dependencies,
at least in my simple implementation, which re-runs the dependency
resolution loop until no new pages are rebuilt.
+ (I added an optimisation that gets it down to 1.5X as much work on
+ average, still 2x as much worst case.)
* Causes extra work for some transitive dependencies that we don't
actually care about. For example, changing index causes
plugins/brokenlinks to update in the first pass; if there's a second