feat(prBody): Support templates in changelogUrl (renovatebot#35380)

Author: neumantm

docs/usage/configuration-options.md

@@ -2738,6 +2738,19 @@ To read the changelogs you must use the link.
 }
 ```
 
+`changelogUrl` supports template compilation.
+
+```json title="Setting the changelog URL for the dummy package using a template"
+{
+  "packageRules": [
+    {
+      "matchPackageNames": ["dummy"],
+      "changelogUrl": "https://github.com/org/monorepo/blob/{{{sourceDirectory}}}/my-custom-changelog.txt"
+    }
+  ]
+}
+```
+
 <!-- prettier-ignore -->
 !!! note
     Renovate can fetch changelogs from Bitbucket, Bitbucket Server / Data Center, Gitea (Forgejo), GitHub and GitLab platforms only, and setting the URL to an unsupported host/platform type won't change that.

lib/workers/repository/update/pr/body/index.spec.ts

@@ -71,6 +71,8 @@ describe('workers/repository/update/pr/body/index', () => {
     });
 
     it('massages upgrades', () => {
+      template.compile.mockImplementation((x) => x);
+
       const upgrade = {
         manager: 'some-manager',
         branchName: 'some-branch',
@@ -172,6 +174,54 @@ describe('workers/repository/update/pr/body/index', () => {
       });
     });
 
+    it('templates changelogUrl', () => {
+      template.compile.mockImplementation((x) =>
+        x === '{{ testTemplate }}'
+          ? 'https://raw.githubusercontent.com/some/templated/CHANGELOG.md'
+          : x,
+      );
+
+      const upgrade = {
+        manager: 'some-manager',
+        branchName: 'some-branch',
+        dependencyUrl: 'https://github.com/foo/bar',
+        sourceUrl: 'https://github.com/foo/bar',
+        sourceDirectory: '/baz',
+        changelogUrl: '{{ testTemplate }}',
+        homepage: 'https://example.com',
+      };
+
+      getPrBody(
+        {
+          manager: 'some-manager',
+          baseBranch: 'base',
+          branchName: 'some-branch',
+          upgrades: [upgrade],
+        },
+        {
+          debugData: {
+            updatedInVer: '1.2.3',
+            createdInVer: '1.2.3',
+            targetBranch: 'base',
+          },
+        },
+        {},
+      );
+
+      expect(upgrade).toMatchObject({
+        branchName: 'some-branch',
+        changelogUrl: '{{ testTemplate }}',
+        depNameLinked:
+          '[undefined](https://example.com) ([source](https://github.com/foo/bar/tree/HEAD/baz), [changelog](https://raw.githubusercontent.com/some/templated/CHANGELOG.md))',
+        dependencyUrl: 'https://github.com/foo/bar',
+        homepage: 'https://example.com',
+        references:
+          '[homepage](https://example.com), [source](https://github.com/foo/bar/tree/HEAD/baz), [changelog](https://raw.githubusercontent.com/some/templated/CHANGELOG.md)',
+        sourceDirectory: '/baz',
+        sourceUrl: 'https://github.com/foo/bar',
+      });
+    });
+
     it('uses dependencyUrl as primary link', () => {
       const upgrade = {
         manager: 'some-manager',

lib/workers/repository/update/pr/body/index.ts

@@ -48,8 +48,11 @@ function massageUpdateMetadata(config: BranchConfig): void {
         `[source](${getFullSourceUrl(sourceUrl, sourceRootPath, sourceDirectory)})`,
       );
     }
-    if (changelogUrl) {
-      otherLinks.push(`[changelog](${changelogUrl})`);
+    const templatedChangelogUrl = changelogUrl
+      ? template.compile(changelogUrl, upgrade, true)
+      : undefined;
+    if (templatedChangelogUrl) {
+      otherLinks.push(`[changelog](${templatedChangelogUrl})`);
     }
     if (otherLinks.length) {
       depNameLinked += ` (${otherLinks.join(', ')})`;
@@ -64,8 +67,8 @@ function massageUpdateMetadata(config: BranchConfig): void {
         `[source](${getFullSourceUrl(sourceUrl, sourceRootPath, sourceDirectory)})`,
       );
     }
-    if (changelogUrl) {
-      references.push(`[changelog](${changelogUrl})`);
+    if (templatedChangelogUrl) {
+      references.push(`[changelog](${templatedChangelogUrl})`);
     }
     upgrade.references = references.join(', ');
   });