fix: remove all containers and images by label on app destroy

Previously, we would filter containers and images by name, which could be fail if the app was renamed or no longer was tagged "correctly" due to a rebuild. Now, we filter by label, ensuring an app is completely cleaned up on deletion.

Also:

- Move docker image cleanup from apps plugin to builder plugin: This isn't where it belongs - images should be cleaned up in a builder plugin (or the builders plugin) and not in the apps plugin, which has nothing to do with docker images anyways.
- Remove the code from the scheduler plugin, as that will only do anything if the scheduler is enabled for the app.
- Bypass image removal if there are no images to remove
- Always delete app containers: The herokuish builder creates intermediate build containers - something that should be refactored - and ideally this gets run in that builder plugin, but keeping the logic here ensures we don't have code duplication. This is otherwise safe as it will be a no-op if there are no containers to clean up.

plugins/apps/functions.go

@@ -1,7 +1,6 @@
 package apps
 
 import (
-	"bytes"
 	"errors"
 	"fmt"
 	"os"
@@ -95,53 +94,6 @@ func destroyApp(appName string) error {
 	return nil
 }
 
-func listImagesByAppLabel(appName string) ([]string, error) {
-	command := []string{
-		common.DockerBin(),
-		"image",
-		"list",
-		"--quiet",
-		"--filter",
-		fmt.Sprintf("label=com.dokku.app-name=%v", appName),
-	}
-
-	var stderr bytes.Buffer
-	listCmd := common.NewShellCmd(strings.Join(command, " "))
-	listCmd.ShowOutput = false
-	listCmd.Command.Stderr = &stderr
-	b, err := listCmd.Output()
-
-	if err != nil {
-		return []string{}, errors.New(strings.TrimSpace(stderr.String()))
-	}
-
-	output := strings.Split(strings.TrimSpace(string(b[:])), "\n")
-	return output, nil
-}
-
-func listImagesByImageRepo(imageRepo string) ([]string, error) {
-	command := []string{
-		common.DockerBin(),
-		"image",
-		"list",
-		"--quiet",
-		imageRepo,
-	}
-
-	var stderr bytes.Buffer
-	listCmd := common.NewShellCmd(strings.Join(command, " "))
-	listCmd.ShowOutput = false
-	listCmd.Command.Stderr = &stderr
-	b, err := listCmd.Output()
-
-	if err != nil {
-		return []string{}, errors.New(strings.TrimSpace(stderr.String()))
-	}
-
-	output := strings.Split(strings.TrimSpace(string(b[:])), "\n")
-	return output, nil
-}
-
 // creates an app if allowed
 func maybeCreateApp(appName string) error {
 	if err := appExists(appName); err == nil {

plugins/apps/triggers.go

@@ -101,19 +101,5 @@ func TriggerPostDelete(appName string) error {
 		common.LogWarn(err.Error())
 	}
 
-	imagesByAppLabel, err := listImagesByAppLabel(appName)
-	if err != nil {
-		common.LogWarn(err.Error())
-	}
-
-	imageRepo := common.GetAppImageRepo(appName)
-	imagesByRepo, err := listImagesByImageRepo(imageRepo)
-	if err != nil {
-		common.LogWarn(err.Error())
-	}
-
-	images := append(imagesByAppLabel, imagesByRepo...)
-	common.RemoveImages(images)
-
 	return nil
 }