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

.cloudbuild/deploy.yaml

@@ -8,6 +8,12 @@ steps:
     args: ['run', 'cloud-secrets']
     env:
     - 'PROJECT_ID=$PROJECT_ID'
+  - name: 'node'
+    entrypoint: npm
+    args: ['run', 'HEAD']
+    env:
+    - 'PROJECT_ID=$PROJECT_ID'
+    - 'BUILD_ID=$BUILD_ID'
   - name: node
     entrypoint: npm
     args: ['run', 'build']

HEAD.js

@@ -0,0 +1,59 @@
+const request = require('request');
+
+/**
+ * @param {string} url
+ * @param {string} [method]
+ * @returns {Promise<*>}
+ */
+const requestPromise = (url, method = 'GET') => {
+  return new Promise((resolve, reject) =>
+    request({url, method}, (e, r) => {
+      let body;
+      try {
+        body = JSON.parse(r.body);
+      } catch {
+        body = r.body;
+      }
+      if (e) {
+        reject(e);
+      } else if (body.error) {
+        reject(body);
+      } else {
+        resolve(body);
+      }
+    }),
+  );
+};
+
+(async () => {
+  let deployedHEAD;
+  try {
+    deployedHEAD = await requestPromise('https://web.dev/HEAD');
+  } catch {
+    deployedHEAD = "COULDN'T GET DEPLOYED HEAD";
+  }
+  const currentHEAD = require('child_process')
+    .execSync('git rev-parse HEAD')
+    .toString()
+    .trim();
+
+  console.log(`Current HEAD: ${currentHEAD}`);
+  console.log(`Deployed HEAD: ${deployedHEAD}`);
+
+  if (currentHEAD === currentHEAD) {
+    console.log('The current and deployed HEADs are the same, stopping build.');
+    const projectId = process.env.PROJECT_ID;
+    const id = process.env.BUILD_ID;
+    const projectsBuildCancel = `https://cloudbuild.googleapis.com/v1/projects/${projectId}/builds/${id}:cancel`;
+    try {
+      const cancelledBuild = await requestPromise(projectsBuildCancel, 'POST');
+      console.log('CANCELLED BUILD', cancelledBuild);
+    } catch (e) {
+      console.log('FAILED TO CANCEL BUILD', e);
+    }
+  } else {
+    console.log(
+      'The current and deployed HEADs are different, continuing build.',
+    );
+  }
+})();

gulp-tasks/write-head.js

@@ -0,0 +1,18 @@
+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 = require('child_process')
+      .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,
   ),
 );