TL;DR: I'm proposing deprecating a bunch of parameters. See https://phabricator.wikimedia.org/T164106.

In the action API, there are two ways to parse a page/revision: using action=parse, or using the rvparse parameter to action=query&prop=revisions. Similarly, there are two ways to get a diff: using action=compare, or using parameters such as rvdiffto to action=query&prop=revisions. And then there's action=expandtemplates versus the rvexpandtemplates parameter to prop=revisions. This is a somewhat annoying bit of code duplication.

Further, the prop=revisions versions of these features have somewhat strange behavior. rvparse forces rvlimit=1. rvdiffto and related parameters will sometimes output "notcached" with no way to directly handle the situation.

So, I propose deprecating all of these parameters. The parameters that would be deprecated are the 'rvdifftotext', 'rvdifftotextpst', 'rvdiffto', 'rvexpandtemplates', 'rvgeneratexml', 'rvparse', and 'rvprop=parsetree' parameters to prop=revisions, and the similarly named parameters to prop=deletedrevisions, list=allrevisions, and list=alldeletedrevisions.

Following the normal action API deprecation policy, they'd output warnings but would continue to function until usage drops sufficiently or until it becomes too much trouble to fix them, and they wouldn't receive new feature development. If anyone would object to this plan, please reply at https://phabricator.wikimedia.org/T164106, or here if you really hate Phabricator. If there aren't major objections, I'll probably do the deprecation in the next week or two. Thanks.