feat: support chaos commits on deploy

See coop-cloud/organising#517

cli/app/rollback.go

@@ -36,11 +36,16 @@ var appRollbackCommand = cli.Command{
 	Description: `
 This command rolls an app back to a previous version.
 
-You may pass "--force/-f" to downgrade to the same version again. This can be
-useful if the container runtime has gotten into a weird state.
+Unlike "deploy", chaos operations are not supported here. Only recipe versions
+are supported values for "[<version>]".
 
-This action could be destructive, please ensure you have a copy of your app
-data beforehand.`,
+A rollback can be destructive, please ensure you have a copy of your app data
+beforehand.
+
+EXAMPLE:
+
+    abra app rollback foo.example.com
+    abra app rollback foo.example.com 1.2.3+3.2.1`,
 	BashComplete: autocomplete.AppNameComplete,
 	Action: func(c *cli.Context) error {
 		app := internal.ValidateApp(c)
@@ -169,7 +174,7 @@ data beforehand.`,
 		}
 
 		log.Debugf("choosing %s as version to rollback", chosenDowngrade)
-		if err := app.Recipe.EnsureVersion(chosenDowngrade); err != nil {
+		if _, err := app.Recipe.EnsureVersion(chosenDowngrade); err != nil {
 			log.Fatal(err)
 		}