Actually remove reviewers instead of just removing it from the Gerald…

… comment (#37)

## Summary:
In the past, if someone commented `#RemoveMe` on a pull request, it would remove them from the Gerald megacomment and prevent Gerald from readding them as reviewers in the future, but it doesn't actually remove them as a reviewer. This PR makes it so that Gerald will actually make a request to remove reviewers that have commented `#RemoveMe`.

Issue: WEB-2758

## Test plan:
See (#35), where Kevin B. was requested for review, and after commenting `#RemoveMe`, his review request was removed.

Author: yipstanley

Reviewers: jeresig

Required Reviewers: 

Approved by: jeresig

Checks: ✅ Flow Coverage, ✅ Jest Coverage, ✅ Jest, ✅ Eslint, ✅ autofix, ✅ lint_and_unit, ✅ build_index

Pull request URL: #37

src/runOnPullRequest.js

@@ -9,6 +9,7 @@ import {
     parseExistingComments,
     getFilteredLists,
     makeCommentBody,
+    maybeRemoveReviewRequests,
 } from './utils';
 import {execCmd} from './execCmd';
 import {ownerAndRepo, context, extraPermGithub} from './setup';
@@ -100,6 +101,11 @@ export const runOnPullRequest = async () => {
         removedJustNames,
     );
 
+    await maybeRemoveReviewRequests(
+        removedJustNames,
+        {...ownerAndRepo, pull_number: context.issue.number},
+        extraPermGithub,
+    );
     await extraPermGithub.pulls.createReviewRequest({
         ...ownerAndRepo,
         pull_number: context.issue.number,

src/utils.js

@@ -1,6 +1,10 @@
 // @flow
 
-import {type Octokit$IssuesListCommentsResponseItem, type Octokit$Response} from '@octokit/rest';
+import {
+    type Octokit,
+    type Octokit$IssuesListCommentsResponseItem,
+    type Octokit$Response,
+} from '@octokit/rest';
 import fs from 'fs';
 import fg from 'fast-glob'; // flow-uncovered-line
 
@@ -75,6 +79,33 @@ const filterIgnoreFiles = (fileContents: string): Array<string> => {
     });
 };
 
+/**
+ * @desc If any of the usernames in removedJustNames are reviewers, we should also
+ * remove them as a reviewer.
+ *
+ * @param removedJustNames - Just the usernames (not including @) of the people
+ * who have requeseted to be removed.
+ * @param params - The owner, repo, and pull_number parameters for Octokit requests.
+ * They can't be imported, because that would make this file really difficult to test.
+ * @param githubClient - The Octokit client that we can make calls on. We also can't import this.
+ */
+export const maybeRemoveReviewRequests = async (
+    removedJustNames: Array<string>,
+    params: {owner: string, repo: string, pull_number: number},
+    githubClient: Octokit,
+) => {
+    const {data: reviewRequests} = await githubClient.pulls.listReviewRequests({...params});
+    const toRemove = reviewRequests.users
+        .filter(user => removedJustNames.includes(user.login))
+        .map(user => user.login);
+    if (toRemove.length) {
+        await githubClient.pulls.deleteReviewRequest({
+            ...params,
+            reviewers: toRemove,
+        });
+    }
+};
+
 /**
  * @desc Read ./.geraldignore and ./.gitignore if they exist.
  * Split the files by newlines to serve as the list of files/directories to