move alpha.dagger.io/europa to dagger.io

Signed-off-by: Andrea Luzzardi <aluzzardi@gmail.com>

pkg/dagger.io/dagger/utils.cue

@@ -0,0 +1,28 @@
+package dagger
+
+import (
+	"alpha.dagger.io/europa/dagger/engine"
+)
+
+// Select a subdirectory from a filesystem tree
+#Subdir: {
+	// Input tree
+	input: #FS
+
+	// Path of the subdirectory
+	// Example: "/build"
+	path: string
+
+	// Subdirectory tree
+	output: #FS & copy.output
+
+	// Copy action
+	copy: engine.#Copy & {
+		"input": engine.#Scratch
+		source: {
+			root:   input
+			"path": path
+		}
+		dest: "/"
+	}
+}