clfilter: introduces a hidden filter This filter exclude all hidden revision. We plan to use this filter to hide revision instead of manually checking contents of the hidden revisions set.

perftest: allow selection of volatile set to benchmark This helps when you focus on a subset of the volatile chain.

perftest: add a command to benchmark construction of volatile cache Obsolescence and filtering related caches are critical. Having a handy way to check them is valuable.

perftest: add an option to invalidate volatile cache Some revsets are sensitive to such initialization. Being able to test the impact is great.

perftest: document the perfrevset command I'll add an argument to it.

perftest: migrate to new style command declaration Declaring synopsis and argument on the function site is much clearer.

perftest: drop duplicated codes The `perfnodelookup` lookup commands is duplicated. We drop the first version, overwritten by the seconds.