feat: write undeploy version

See toolshed/organising#633

cli/app/undeploy.go

@@ -21,7 +21,7 @@ var AppUndeployCommand = &cobra.Command{
 	Use:     "undeploy <app> [flags]",
 	Aliases: []string{"un"},
 	Short:   "Undeploy an app",
-	Long: `This does not destroy any of the application data.
+	Long: `This does not destroy any application data.
 
 However, you should remain vigilant, as your swarm installation will consider
 any previously attached volumes as eligible for pruning once undeployed.
@@ -79,6 +79,11 @@ Passing "--prune/-p" does not remove those volumes.`,
 				log.Fatal(err)
 			}
 		}
+
+		log.Debugf("choosing %s as version to save to env file", deployMeta.Version)
+		if err := app.WriteRecipeVersion(deployMeta.Version, false); err != nil {
+			log.Fatalf("writing undeployed recipe version in env file: %s", err)
+		}
 	},
 }