feat(upgrade): add --releasenotes: show release notes and skip upgrading

cli/app/upgrade.go

@@ -31,6 +31,7 @@ var appUpgradeCommand = cli.Command{
 		internal.NoDomainChecksFlag,
 		internal.DontWaitConvergeFlag,
 		internal.OfflineFlag,
+		internal.ReleaseNotesFlag,
 	},
 	Before: internal.SubCommandBefore,
 	Description: `
@@ -269,6 +270,12 @@ recipes.
 			}
 		}
 
+		if internal.ReleaseNotes {
+			fmt.Println()
+			fmt.Print(releaseNotes)
+			return nil
+		}
+
 		if err := internal.NewVersionOverview(app, deployedVersion, chosenUpgrade, releaseNotes); err != nil {
 			logrus.Fatal(err)
 		}