d2cli: Move main code into d2cli so it can be imported from tests

Updates terrastruct#903

cli-e2etests/main_test.go

@@ -0,0 +1,34 @@
+package main_test
+
+import (
+	"context"
+	"testing"
+	"time"
+)
+
+func TestCLI_E2E(t *testing.T) {
+	t.Parallel()
+
+	tca := []struct {
+		name string
+		run  func(t *testing.T, ctx context.Context)
+	}{
+		{
+			name: "hello_world",
+			run:  func(t *testing.T, ctx context.Context) {},
+		},
+	}
+
+	ctx := context.Background()
+	for _, tc := range tca {
+		tc := tc
+		t.Run(tc.name, func(t *testing.T) {
+			t.Parallel()
+
+			ctx, cancel := context.WithTimeout(ctx, time.Minute*5)
+			defer cancel()
+
+			tc.run(t, ctx)
+		})
+	}
+}

fmt.go → d2cli/fmt.go

@@ -1,4 +1,4 @@
-package main
+package d2cli
 
 import (
 	"bytes"

help.go → d2cli/help.go

@@ -1,4 +1,4 @@
-package main
+package d2cli
 
 import (
 	"context"