merge.applyupdates: use counters from mergestate This eliminates a whole bunch of duplicate code and allows us to update the removed count for change/delete conflicts where the delete action was chosen.

mergestate: add a function to return the number of unresolved files Note that unlike the other functions, this is based on the persistent mergestate.

mergestate: add a method to return updated/merged/removed counts This will not only allow us to remove a bunch of duplicate code in applyupdates in an upcoming patch, it will also allow the resolve interface to be a lot simpler: it doesn't need to return the dirstate action to applyupdates.

mergestate._resolve: don't return the action any more This is a partial backout of an earlier diff -- now that we're storing the results in a dict, we don't actually need this any more.

mergestate._resolve: store return code and action for each file We're going to need this to compute (a) updated/merged/unresolved counts, and (b) actions to perform on the dirstate.

revsetbenchmarks: support benchmarking changectx loading Many revset consumers construct changectx instances for each returned result. Add support for benchmarking this to our revset benchmark script. In the future, we might want to have some kind of special syntax in the parsed revset files to engage this mode automatically. This would enable us to load changectxs for revsets that do that in the code and would more accurately benchmark what's actually happening. For now, running all revsets with or without changectxs is sufficient.

perf: support obtaining contexts from perfrevset Previously, perfrevset called repo.revs(), which only returns integer revisions. Many revset consumers call repo.set(), which returns changectx instances. Or they obtain a context manually later. Since obtaining changectx instances when evaluating revsets is common, this patch adds support for benchmarking this use case. While we added an if conditional for every benchmark loop, it doesn't appear to matter since revset evaluation dwarfs the cost of a single if.

localrepo: improve docstring for revset methods revs() doesn't return a list. Also document what its arguments do. Also clarify that set() is just a convenience wrapper around revs().

revlog: improve documentation There are a lot of functions and variables doing similar things. Document the role and functionality of each to make it easier to grok.

demandimport: don't enable when running under PyPy On demand importing doesn't work with PyPy for some reason. Don't honor requests to enable demand importing when running under PyPy.