fix: use package name to build aggregate if present

__snapshots__/merge.js

@@ -41,6 +41,25 @@ exports['Merge plugin run merges multiple pull requests into an aggregate 1'] =
 ---
 
 
+<details><summary>python-pkg: 1.0.0</summary>
+
+Release notes for path: python, releaseType: python
+</details>
+
+<details><summary>@here/pkgA: 3.3.4</summary>
+
+Release notes for path: node, releaseType: node
+</details>
+
+---
+This PR was generated with [Release Please](https://github.com/googleapis/release-please). See [documentation](https://github.com/googleapis/release-please#release-please).
+`
+
+exports['Merge plugin run merges multiple pull requests into an aggregate and uses packageName as default for branch name if present 1'] = `
+:robot: I have created a release *beep* *boop*
+---
+
+
 <details><summary>python-pkg: 1.0.0</summary>
 
 Release notes for path: python, releaseType: python

src/manifest.ts

@@ -776,6 +776,9 @@ export class Manifest {
         ) {
           mergeOptions.pullRequestFooter = config.pullRequestFooter;
         }
+        if ('packageName' in config) {
+          mergeOptions.packageName = config.packageName;
+        }
       }
       this.plugins.push(
         new Merge(

src/plugins/merge.ts

@@ -27,6 +27,7 @@ import {mergeUpdates} from '../updaters/composite';
 import {GitHub} from '../github';
 
 export interface MergeOptions {
+  packageName?: string;
   pullRequestTitlePattern?: string;
   pullRequestHeader?: string;
   pullRequestFooter?: string;
@@ -46,6 +47,7 @@ export class Merge extends ManifestPlugin {
   private pullRequestFooter?: string;
   private headBranchName?: string;
   private forceMerge: boolean;
+  private packageName: string;
 
   constructor(
     github: GitHub,
@@ -60,6 +62,7 @@ export class Merge extends ManifestPlugin {
     this.pullRequestFooter = options.pullRequestFooter;
     this.headBranchName = options.headBranchName;
     this.forceMerge = options.forceMerge ?? false;
+    this.packageName = options.packageName ?? '';
   }
 
   async run(
@@ -83,7 +86,6 @@ export class Merge extends ManifestPlugin {
       },
       [[], []]
     );
-
     const releaseData: ReleaseData[] = [];
     const labels = new Set<string>();
     let rawUpdates: Update[] = [];
@@ -100,7 +102,6 @@ export class Merge extends ManifestPlugin {
       }
     }
     const updates = mergeUpdates(rawUpdates);
-
     const pullRequest = {
       title: PullRequestTitle.ofComponentTargetBranchVersion(
         rootRelease?.pullRequest.title.component,
@@ -117,7 +118,12 @@ export class Merge extends ManifestPlugin {
       labels: Array.from(labels),
       headRefName:
         this.headBranchName ??
-        BranchName.ofTargetBranch(this.targetBranch).toString(),
+        (this.packageName
+          ? BranchName.ofComponentTargetBranch(
+              this.packageName,
+              this.targetBranch
+            ).toString()
+          : BranchName.ofTargetBranch(this.targetBranch).toString()),
       draft: !candidates.some(candidate => !candidate.pullRequest.draft),
     };
 

test/plugins/merge.ts

@@ -97,6 +97,53 @@ describe('Merge plugin', () => {
       assertHasUpdate(updates, 'path1/foo', CompositeUpdater);
       assertHasUpdate(updates, 'path2/foo', RawContent);
       snapshot(dateSafe(candidate!.pullRequest.body.toString()));
+      expect(
+        newCandidates[0].pullRequest.headRefName ===
+          'release-please--branches--main'
+      );
+    });
+
+    it('merges multiple pull requests into an aggregate and uses packageName as default for branch name if present', async () => {
+      const candidates: CandidateReleasePullRequest[] = [
+        buildMockCandidatePullRequest('python', 'python', '1.0.0', {
+          component: 'python-pkg',
+          updates: [
+            {
+              path: 'path1/foo',
+              createIfMissing: false,
+              updater: new RawContent('foo'),
+            },
+          ],
+        }),
+        buildMockCandidatePullRequest('node', 'node', '3.3.4', {
+          component: '@here/pkgA',
+          updates: [
+            {
+              path: 'path1/foo',
+              createIfMissing: false,
+              updater: new RawContent('bar'),
+            },
+            {
+              path: 'path2/foo',
+              createIfMissing: false,
+              updater: new RawContent('asdf'),
+            },
+          ],
+        }),
+      ];
+      const plugin = new Merge(github, 'main', {}, {packageName: '@here/pkgA'});
+      const newCandidates = await plugin.run(candidates);
+      expect(newCandidates).lengthOf(1);
+      const candidate = newCandidates[0];
+      const updates = candidate!.pullRequest.updates;
+      expect(updates).lengthOf(2);
+      assertHasUpdate(updates, 'path1/foo', CompositeUpdater);
+      assertHasUpdate(updates, 'path2/foo', RawContent);
+      snapshot(dateSafe(candidate!.pullRequest.body.toString()));
+      expect(
+        newCandidates[0].pullRequest.headRefName ===
+          'release-please--branches--main--components--@here/pkgA'
+      );
     });
 
     it('merges multiple pull requests as a draft', async () => {