feat(wanda): Add dependency graph with @name discovery

Add buildDepGraph() to parse wanda specs and resolve @name dependencies
by scanning the repo for *.wanda.yaml files. The dependency graph is
built in deterministic topological order using Kahn's algorithm with
lexicographic tie-breaking.

Key features:
- @name syntax in froms references local specs by name
- Automatic discovery by scanning repo from git root
- Parallel spec parsing for performance
- Cycle detection with helpful error messages
- Variable expansion with unexpanded var detection

Topic: wanda-deps

Signed-off-by: andrew <andrew@anyscale.com>

Author: andrew-anyscale

wanda/deps.go

@@ -172,7 +172,7 @@ func TestForge_withHints(t *testing.T) {
 		t.Fatalf("build: %v", err)
 	}
 
-	const tag = "cr.ray.io/rayproject/hello"
+	const tag = "cr.ray.io/rayproject/hello-hint"
 
 	ref, err := name.ParseReference(tag)
 	if err != nil {
@@ -214,11 +214,11 @@ func TestForge(t *testing.T) {
 		NamePrefix: "cr.ray.io/rayproject/",
 	}
 
-	if err := Build("testdata/hello.wanda.yaml", config); err != nil {
+	if err := Build("testdata/hello-test.wanda.yaml", config); err != nil {
 		t.Fatalf("build: %v", err)
 	}
 
-	const tag = "cr.ray.io/rayproject/hello"
+	const tag = "cr.ray.io/rayproject/hello-test"
 
 	ref, err := name.ParseReference(tag)
 	if err != nil {
@@ -283,7 +283,7 @@ func TestForge_noCache(t *testing.T) {
 		t.Fatalf("build: %v", err)
 	}
 
-	const tag = "cr.ray.io/rayproject/hello"
+	const tag = "cr.ray.io/rayproject/hello-nocache"
 
 	ref, err := name.ParseReference(tag)
 	if err != nil {
@@ -362,7 +362,7 @@ func TestForgeWithRemoteWorkRepo(t *testing.T) {
 		Epoch:      "1",
 	}
 
-	if err := Build("testdata/hello.wanda.yaml", config); err != nil {
+	if err := Build("testdata/hello-test.wanda.yaml", config); err != nil {
 		t.Fatalf("build hello: %v", err)
 	}
 
@@ -405,7 +405,7 @@ func TestForgeWithRemoteWorkRepo(t *testing.T) {
 		t.Fatalf("make new forge: %v", err)
 	}
 
-	helloSpec, err := parseSpecFile("testdata/hello.wanda.yaml")
+	helloSpec, err := parseSpecFile("testdata/hello-test.wanda.yaml")
 	if err != nil {
 		t.Fatalf("parse hello spec: %v", err)
 	}
@@ -420,7 +420,7 @@ func TestForgeWithRemoteWorkRepo(t *testing.T) {
 		t.Errorf("got %d cache hits, want 1", hit)
 	}
 
-	hello := fmt.Sprintf("%s/work:def456-hello", crAddr)
+	hello := fmt.Sprintf("%s/work:def456-hello-test", crAddr)
 	helloRef, err := name.ParseReference(hello)
 	if err != nil {
 		t.Fatalf("parse hello reference: %v", err)
@@ -475,7 +475,7 @@ func TestForgeLocal_withNamePrefix(t *testing.T) {
 		Epoch:      randomEpoch(),
 	}
 
-	if err := Build("testdata/hello.wanda.yaml", config); err != nil {
+	if err := Build("testdata/hello-test.wanda.yaml", config); err != nil {
 		t.Fatalf("build hello: %v", err)
 	}
 
@@ -518,7 +518,7 @@ func TestForgeLocal_withNamePrefix(t *testing.T) {
 		t.Fatalf("make new forge: %v", err)
 	}
 
-	helloSpec, err := parseSpecFile("testdata/hello.wanda.yaml")
+	helloSpec, err := parseSpecFile("testdata/hello-test.wanda.yaml")
 	if err != nil {
 		t.Fatalf("parse hello spec: %v", err)
 	}
@@ -531,7 +531,7 @@ func TestForgeLocal_withNamePrefix(t *testing.T) {
 		t.Errorf("got %d cache hits, want 1", hit)
 	}
 
-	hello := "localhost:5000/rayci-work:abc123-hello"
+	hello := "localhost:5000/rayci-work:abc123-hello-test"
 	helloRef, err := name.ParseReference(hello)
 	if err != nil {
 		t.Fatalf("parse hello reference: %v", err)

wanda/deps_test.go

@@ -0,0 +1,2 @@
+FROM scratch
+COPY Dockerfile.dep-base /opt/

wanda/forge_test.go

@@ -0,0 +1,2 @@
+FROM dep-base
+COPY world.txt /opt/

wanda/testdata/Dockerfile.dep-base

@@ -0,0 +1,2 @@
+FROM dep-middle
+COPY Dockerfile.dep-top /opt/

wanda/testdata/Dockerfile.dep-middle

@@ -1,3 +1,3 @@
-FROM cr.ray.io/rayproject/hello
+FROM cr.ray.io/rayproject/hello-test
 
 COPY world.txt /opt/app/world.txt

wanda/testdata/Dockerfile.dep-top

@@ -0,0 +1,2 @@
+name: dep-base
+dockerfile: Dockerfile.dep-base

wanda/testdata/Dockerfile.world

@@ -0,0 +1,5 @@
+name: dep-middle
+froms: ["cr.ray.io/rayproject/dep-base"]
+dockerfile: Dockerfile.dep-middle
+srcs:
+  - world.txt

wanda/testdata/dep-base.wanda.yaml

@@ -0,0 +1,3 @@
+name: dep-top
+froms: ["cr.ray.io/rayproject/dep-middle"]
+dockerfile: Dockerfile.dep-top