Work in progress: re-write changelog.com example for Europa

Signed-off-by: Solomon Hykes <solomon@dagger.io>

europa-universe/docker/build.cue

@@ -13,28 +13,41 @@ import (
 	// Generate build DAG from linerar steps
 	dag: {
 		for idx, step in steps {
-			// As a special case, wrap #Run into a valid step
-			if step.run != _|_ {
-				"\(idx)": {
-					input: _
-					run:   step & {
-						image: input
-						output: rootfs: _
-					}
-					output: {
-						config: input.config
-						rootfs: run.output.rootfs
-					}
-				}
-			}
+			///// FIXME: this section is broken and in the middle of debug + rewrite
+			//// // 1. image -> input
+			//// if (step.input == _|_) && ((step.image & #Image) != _|_) {
+			////  input: image
+			//// }
 
-			// Otherwise, just use the step as is
-			if step.run == _|_ {
-				"\(idx)": {
-					run: false
-					step
-				}
-			}
+			//// // 2. 
+			//// if ((step.output & docker.#Image) == _|_) && ((step.output.rootfs & dagger.#FS) != _|_) {
+			////  
+			//// }
+
+			//// // As a special case, wrap #Run into a valid step
+			//// if step.run != _|_ {
+			////  "\(idx)": {
+			////   input: _
+			////   run:   step & {
+			////    image: input
+			////    output: rootfs: _
+			////   }
+			////   output: {
+			////    config: input.config
+			////    rootfs: run.output.rootfs
+			////   }
+			////  }
+			//// }
+
+			//// // Otherwise, just use the step as is
+			//// if step.run == _|_ {
+			////  "\(idx)": {
+			////   run: false
+			////   step
+			////  }
+			//// }
+
+			"\(idx)": step
 
 			// Either way, connect input to previous output
 			if idx > 0 {

europa-universe/docker/docker.cue

@@ -19,8 +19,8 @@ import (
 
 // Run a command in a container
 #Run: {
-	run:   true // FIXME
 	image: #Image
+	input: image // for compatibility with #Build
 
 	always: bool | *false
 
@@ -104,7 +104,10 @@ import (
 			message: string | *null
 		}
 
-		output: {
+		output?: {
+			// FIXME: hack for #Build compatibility
+			#Image
+
 			rootfs?: dagger.#FS & _exec.output
 			files: [path=string]: {
 				contents: string