fix: add cl num in release note (#2156)

Fixes #2112

Author: JoeWang1127

internal/librarian/release_notes.go

@@ -75,7 +75,11 @@ Language Image: {{.ImageVersion}}
 {{ range .CommitSections }}
 ### {{.Heading}}
 {{ range .Commits }}
+{{ if index .Footers "PiperOrigin-RevId" -}}
+* {{.Subject}} (PiperOrigin-RevId: {{index .Footers "PiperOrigin-RevId"}}) ([{{shortSHA .SHA}}]({{"https://github.com/"}}{{$noteSection.RepoOwner}}/{{$noteSection.RepoName}}/commit/{{.SHA}}))
+{{- else -}}
 * {{.Subject}} ([{{shortSHA .SHA}}]({{"https://github.com/"}}{{$noteSection.RepoOwner}}/{{$noteSection.RepoName}}/commit/{{.SHA}}))
+{{- end }}
 {{ end }}
 
 {{- end }}

internal/librarian/release_notes_test.go

@@ -536,6 +536,58 @@ Language Image: go:1.21
 
 * a bug fix ([fedcba0](https://github.com/owner/repo/commit/fedcba0987654321000000000000000000000000))
 
+</details>`,
+				librarianVersion, today),
+		},
+		{
+			name: "single library release, with cl num",
+			state: &config.LibrarianState{
+				Image: "go:1.21",
+				Libraries: []*config.LibraryState{
+					{
+						ID: "my-library",
+						// this is the NewVersion in the release note.
+						Version:         "1.1.0",
+						PreviousVersion: "1.0.0",
+						Changes: []*conventionalcommits.ConventionalCommit{
+							{
+								Type:    "feat",
+								Subject: "new feature",
+								SHA:     hash1.String(),
+								Footers: map[string]string{
+									"PiperOrigin-RevId": "123456",
+								},
+							},
+							{
+								Type:    "fix",
+								Subject: "a bug fix",
+								SHA:     hash2.String(),
+								Footers: map[string]string{
+									"PiperOrigin-RevId": "987654",
+								},
+							},
+						},
+						ReleaseTriggered: true,
+					},
+				},
+			},
+			repo: &MockRepository{
+				RemotesValue: []*git.Remote{git.NewRemote(nil, &gitconfig.RemoteConfig{Name: "origin", URLs: []string{"https://github.com/owner/repo.git"}})},
+			},
+			wantReleaseNote: fmt.Sprintf(`Librarian Version: %s
+Language Image: go:1.21
+<details><summary>my-library: 1.1.0</summary>
+
+## [1.1.0](https://github.com/owner/repo/compare/my-library-1.0.0...my-library-1.1.0) (%s)
+
+### Features
+
+* new feature (PiperOrigin-RevId: 123456) ([1234567](https://github.com/owner/repo/commit/1234567890abcdef000000000000000000000000))
+
+### Bug Fixes
+
+* a bug fix (PiperOrigin-RevId: 987654) ([fedcba0](https://github.com/owner/repo/commit/fedcba0987654321000000000000000000000000))
+
 </details>`,
 				librarianVersion, today),
 		},