Migrate PR stats action into Next.js repo (vercel#13177)

* Migrate PR stats into Next.js repo

* Update running prettier in local mode

.eslintignore

@@ -8,3 +8,4 @@ packages/next/compiled/**/*
 packages/react-refresh-utils/**/*.js
 packages/react-dev-overlay/lib/**
 **/__tmp__/**
+.github/actions/next-stats-action/.work

.github/actions/next-stats-action/.gitignore

@@ -0,0 +1,3 @@
+**/node_modules
+out.md
+.work

.github/actions/next-stats-action/Dockerfile

@@ -0,0 +1,19 @@
+FROM node:10-buster
+
+LABEL com.github.actions.name="Next.js PR Stats"
+LABEL com.github.actions.description="Compares stats of a PR with the main branch"
+LABEL repository="https://github.com/zeit/next-stats-action"
+
+COPY . /next-stats
+
+# Install node_modules
+RUN cd /next-stats && yarn install --production
+
+RUN git config --global user.email 'stats@localhost'
+RUN git config --global user.name 'next stats'
+
+RUN apt update
+RUN apt install apache2-utils -y
+
+COPY entrypoint.sh /entrypoint.sh
+ENTRYPOINT ["/entrypoint.sh"]

.github/actions/next-stats-action/README.md

@@ -0,0 +1,93 @@
+# Next.js Stats GitHub Action
+
+> Downloads and runs project with provided configs gathering stats to compare branches
+
+See it in action at Next.js https://github.com/zeit/next.js
+
+## Getting Started
+
+1. Add a `.stats-app` folder to your project with a [`stats-config.js`](#stats-config) and any files to run against for example a test app that is to be built
+2. Add the action to your [workflow](https://help.github.com/en/articles/configuring-a-workflow)
+3. Enjoy the stats
+
+## Stats Config
+
+```TypeScript
+const StatsConfig = {
+  // the Heading to show at the top of stats comments
+  commentHeading: 'Stats from current PR' | undefined,
+  commentReleaseHeading: 'Stats from current release' | undefined,
+  // the command to build your project if not done on post install
+  initialBuildCommand: undefined | string,
+  skipInitialInstall: undefined | boolean,
+  // the command to build the app (app source should be in `.stats-app`)
+  appBuildCommand: string,
+  appStartCommand: string | undefined,
+  // the main branch to compare against (what PRs will be merging into)
+  mainBranch: 'canary',
+  // the main repository path (relative to https://github.com/)
+  mainRepo: 'zeit/next.js',
+  // whether to attempt auto merging the main branch into PR before running stats
+  autoMergeMain: boolean | undefined,
+  // an array of configs for each run
+  configs: [
+    { // first run's config
+      // title of the run
+      title: 'fastMode stats',
+      // whether to diff the outputted files (default: onOutputChange)
+      diff: 'onOutputChange' | false | undefined,
+      // config files to add before running diff (if `undefined` uses `configFiles`)
+      diffConfigFiles: [] | undefined,
+      // renames to apply to make file names deterministic
+      renames: [
+        {
+          srcGlob: 'main-*.js',
+          dest: 'main.js'
+        }
+      ],
+      // config files to add before running (removed before successive runs)
+      configFiles: [
+        {
+          path: './next.config.js',
+          content: 'module.exports = { fastMode: true }'
+        }
+      ],
+      // an array of file groups to diff/track
+      filesToTrack: [
+        {
+          name: 'Pages',
+          globs: [
+            'build/pages/**/*.js'
+          ]
+        }
+      ],
+      // an array of URLs to fetch while `appStartCommand` is running
+      // will be output to fetched-pages/${pathname}.html
+      pagesToFetch: [
+        'https://localhost:$PORT/page-1'
+      ]
+    },
+    { // second run's config
+      title: 'slowMode stats',
+      diff: false,
+      configFiles: [
+        {
+          path: './next.config.js',
+          content: 'module.exports = { slowMode: true }'
+        }
+      ],
+      filesToTrack: [
+        {
+          name: 'Main Bundles',
+          globs: [
+            'build/runtime/webpack-*.js',
+            'build/runtime/main-*.js',
+          ]
+        }
+      ]
+    },
+  ]
+}
+
+module.exports = StatsConfig
+```

.github/actions/next-stats-action/entrypoint.sh

@@ -0,0 +1,6 @@
+#!/bin/bash
+set -eu # stop on error
+
+export HOME=/root
+
+node /next-stats/src/index.js

.github/actions/next-stats-action/package.json

@@ -0,0 +1,18 @@
+{
+  "name": "get-stats",
+  "version": "1.0.0",
+  "main": "src/index.js",
+  "license": "MIT",
+  "dependencies": {
+    "async-sema": "^3.1.0",
+    "fs-extra": "^8.1.0",
+    "get-port": "^5.0.0",
+    "glob": "^7.1.4",
+    "gzip-size": "^5.1.1",
+    "minimatch": "^3.0.4",
+    "node-fetch": "^2.6.0",
+    "prettier": "^1.18.2",
+    "pretty-bytes": "^5.3.0",
+    "pretty-ms": "^5.0.0"
+  }
+}