Describe the feature or problem you’d like to solve

Scenario:

• I've raised a PR, requested reviews, one or more reviewers has requested changes
• I've checked out the PR branch (handily via gh pr checkout...) and made the appropriate changes and pushed them

At the moment, it looks like I can't then request a re-review other than opening the PR in a browser and clicking the "request re-review" next to each reviewer.

It would be really nice, once I've made suitable changes and pushed them, to be able to request re-review via the gh cli tool rather than having to open the PR in a browser and click the request re-review button next to the reviewer(s) who requested changes.

Proposed solution

Maybe something like gh pr request-rereview or something like that? Not sure whether it should automatically request a re-review from all reviewers who had requested changes, or present a list of them if there were more than one and let you select which reviewer(s) you'd like to request a re-review from. (Presumably if there is only one reviewer who requested changes, then just requesting a re-review from them is a no-brainer.)

Might turn out to not be particularly easy, though, as looking at https://developer.github.com/v3/pulls/reviews/ I don't see an API route to request a re-review, so if it's not exposed via the API... In case it helps, looking at what the web interface does when I request a re-review, it triggers a POST to https://github.com/owner/repo/pull/123/review-requests?pr_global_id=xxx with re_request_reviewer_id set.