moved to spec because engine.#Copy is currently unimplemented

Signed-off-by: Richard Jones <richard@dagger.io>

stdlib/europa/dagger/engine/spec/engine/utils.cue

@@ -0,0 +1,26 @@
+package dagger
+
+import (
+	"alpha.dagger.io/europa/dagger/engine/spec/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: engine.#Copy & {
+		"input": engine.#Scratch.output
+		source: {
+			root:   input
+			"path": path
+		}
+	}
+}