feat(core/seo): support adding git revision in meta (#4561)

src/core/seo.js

@@ -3,10 +3,23 @@
  * This Module adds a metatag description to the document, based on the
  * first paragraph of the abstract.
  */
+import { html } from "../core/import-maps.js";
 
 export const name = "core/seo";
 
-export function run() {
+export function run(conf) {
+  if (conf.gitRevision) {
+    // This allows to set a git revision of the source used to produce the
+    // generated content. Typically, this would be set when generating the
+    // static HTML via a build process.
+    // 'revision' is the name recommended in https://wiki.whatwg.org/wiki/MetaExtensions
+    const metaElem = html`<meta
+      name="revision"
+      content="${conf.gitRevision}"
+    />`;
+    document.head.appendChild(metaElem);
+  }
+
   const firstParagraph = document.querySelector("#abstract p:first-of-type");
   if (!firstParagraph) {
     return; // no abstract, so nothing to do

tests/spec/core/seo-spec.js

@@ -5,6 +5,7 @@ import {
   makeBasicConfig,
   makeDefaultBody,
   makeRSDoc,
+  makeStandardOps,
 } from "../SpecHelper.js";
 
 describe("Core — Seo", () => {
@@ -35,4 +36,14 @@ describe("Core — Seo", () => {
     const meta = doc.head.querySelector("meta[name=description]");
     expect(meta.content).toBe("Pass");
   });
+
+  it("documents a revision in a meta element when set", async () => {
+    const gitRevision = "11223344556677889900aabbccddeeffaabbccddeeff";
+    const doc = await makeRSDoc(
+      makeStandardOps({ specStatus: "ED", group: "webapps", gitRevision })
+    );
+    expect(
+      doc.querySelector(`meta[name='revision'][content='${gitRevision}']`)
+    ).toBeTruthy();
+  });
 });