feat: ✨ Support ${remoteUser} in feature definitions

This change allows using `${remoteUser}` inside of devcontainer-feature.json similar to the exising ${devcontainerId}.

src/spec-common/variableSubstitution.ts

@@ -15,6 +15,7 @@ export interface SubstitutionContext {
 	localWorkspaceFolder?: string;
 	containerWorkspaceFolder?: string;
 	env: NodeJS.ProcessEnv;
+	remoteUser?: string;
 }
 
 export function substitute<T extends object>(context: SubstitutionContext, value: T): T {
@@ -109,6 +110,9 @@ function replaceWithContext(isWindows: boolean, context: SubstitutionContext, ma
 		case 'containerWorkspaceFolderBasename':
 			return context.containerWorkspaceFolder !== undefined ? path.posix.basename(context.containerWorkspaceFolder) : match;
 
+		case 'remoteUser':
+			return context.remoteUser !== undefined ? context.remoteUser : match;
+
 		default:
 			return match;
 	}

src/spec-node/configContainer.ts

@@ -97,6 +97,7 @@ export async function readDevContainerConfigFile(cliHost: CLIHost, workspace: Wo
 		containerWorkspaceFolder: workspaceConfig.workspaceFolder,
 		configFile,
 		env: cliHost.env,
+		remoteUser: updated.remoteUser
 	}, value);
 	const config: DevContainerConfig = substitute0(updated);
 	if (typeof config.workspaceFolder === 'string') {

src/test/configs/image-with-local-feature/.devcontainer/devcontainer.json

@@ -0,0 +1,8 @@
+{
+	"name": "Demo container",
+	"image": "mcr.microsoft.com/devcontainers/base:bullseye",
+	"features": {
+		"./test-feature": {}
+	},
+	"remoteUser": "vscode"
+}

src/test/configs/image-with-local-feature/.devcontainer/test-feature/devcontainer-feature.json

@@ -0,0 +1,14 @@
+{
+	"$schema": "https://raw.githubusercontent.com/devcontainers/spec/main/schemas/devContainerFeature.schema.json",
+	"id": "test-feature",
+	"name": "test-feature",
+	"version": "0.0.1",
+	"description": "Testing a feature",
+	"mounts": [
+		{
+			"source": "test-${devcontainerId}",
+			"target": "/home/${remoteUser}",
+			"type": "volume"
+		}
+	]
+}

src/test/configs/image-with-local-feature/.devcontainer/test-feature/install.sh

@@ -0,0 +1,3 @@
+#!/bin/bash
+
+echo "I am the install script and I do nothing."