feat: teach recipe sync to understand new versions

Closes coop-cloud/organising#177.

pkg/recipe/recipe.go

@@ -41,6 +41,33 @@ func (r Recipe) UpdateTag(image, tag string) error {
 	return nil
 }
 
+// Tags list the recipe tags
+func (r Recipe) Tags() ([]string, error) {
+	var tags []string
+
+	recipeDir := path.Join(config.ABRA_DIR, "apps", r.Name)
+	repo, err := git.PlainOpen(recipeDir)
+	if err != nil {
+		return tags, err
+	}
+
+	gitTags, err := repo.Tags()
+	if err != nil {
+		return tags, err
+	}
+
+	if err := gitTags.ForEach(func(ref *plumbing.Reference) (err error) {
+		tags = append(tags, strings.TrimPrefix(string(ref.Name()), "refs/tags/"))
+		return nil
+	}); err != nil {
+		return tags, err
+	}
+
+	logrus.Debugf("detected '%s' as tags for recipe '%s'", strings.Join(tags, ", "), r.Name)
+
+	return tags, nil
+}
+
 // Get retrieves a recipe.
 func Get(recipeName string) (Recipe, error) {
 	if err := EnsureExists(recipeName); err != nil {