phabricator: change "readpatch" to be more flexible Previously, `readpatch` and `querydrev` take a same `params` and `stack` parameters. This patch changes `readpatch` so it takes the output of `querydrev`, not the input of `querydrev`. This makes the code more flexible and cleaner. Differential Revision: https://phab.mercurial-scm.org/D124