build(git): only deploy site if it's a new commit, fixes #3655

.cloudbuild/deploy.yaml

@@ -1,23 +1,35 @@
 timeout: 2700s # set build timeout to 45 mins
 steps:
   - name: node
+    id: 'Install dependencies'
     entrypoint: npm
     args: ['ci']
   - name: node
+    id: 'Generate .env file'
     entrypoint: npm
     args: ['run', 'cloud-secrets']
     env:
     - 'PROJECT_ID=$PROJECT_ID'
+  - name: 'node'
+    id: 'Verify new commit'
+    entrypoint: npm
+    args: ['run', 'HEAD']
+    env:
+    - 'BUILD_ID=$BUILD_ID'
   - name: node
+    id: 'Build site'
     entrypoint: npm
     args: ['run', 'build']
     env:
     - 'ELEVENTY_ENV=prod'
   - name: node
+    id: 'Configure firebase.json'
     entrypoint: npm
     args: ['run', 'firebase-config']
   - name: 'gcr.io/$PROJECT_ID/firebase'
+    id: 'Deploy site to Firebase'
     args: ['deploy']
   - name: node
+    id: 'Algolia index site'
     entrypoint: npm
     args: ['run', 'algolia']

HEAD.js

@@ -0,0 +1,36 @@
+const request = require('request');
+const {execSync} = require('child_process');
+const {CloudBuildClient} = require('@google-cloud/cloudbuild');
+
+const client = new CloudBuildClient();
+
+/**
+ * @returns {Promise<string>}
+ */
+const getDeployedHead = () => {
+  return new Promise((resolve) =>
+    request('https://web.dev/HEAD', (e, r) => {
+      resolve(r.statusCode >= 400 || e ? '' : r.body);
+    }),
+  );
+};
+
+(async () => {
+  const deployedHEAD = await getDeployedHead();
+  const currentHEAD = execSync('git rev-parse HEAD').toString().trim();
+
+  console.log(`Current HEAD: ${currentHEAD}`);
+  console.log(`Deployed HEAD: ${deployedHEAD}`);
+
+  if (currentHEAD === currentHEAD) {
+    console.log('The current and deployed HEADs are the same, stopping build.');
+    const BUILD_ID = process.env.BUILD_ID;
+    client.cancelBuild({
+      id: BUILD_ID,
+    });
+  } else {
+    console.log(
+      'The current and deployed HEADs are different, continuing build.',
+    );
+  }
+})();

gulp-tasks/write-head.js

@@ -0,0 +1,17 @@
+const {execSync} = require('child_process');
+
+const isProd = process.env.ELEVENTY_ENV === 'prod';
+
+/**
+ * Write the HEAD SHA to the `dist` on prod builds.
+ *
+ * @returns {Promise<void>}
+ */
+const writeHEAD = async () => {
+  if (isProd) {
+    const HEAD = execSync('git rev-parse HEAD').toString().trim();
+    require('fs').writeFileSync('./dist/HEAD', HEAD);
+  }
+};
+
+module.exports = writeHEAD;

gulpfile.js

@@ -21,6 +21,7 @@ const copyFonts = require('./gulp-tasks/copy-fonts.js');
 const copyGlobalImages = require('./gulp-tasks/copy-global-images.js');
 const copyMisc = require('./gulp-tasks/copy-misc.js');
 const sassTask = require('./gulp-tasks/sass.js');
+const writeHead = require('./gulp-tasks/write-head.js');
 
 gulp.task('copy-content-assets', copyContentAssets);
 gulp.task('default-locale', copyDefaultLocale);
@@ -35,6 +36,7 @@ gulp.task(
     copyContentAssets,
     copyFonts,
     sassTask,
+    writeHead,
   ),
 );