more submodule support, diff colorization

extensions/git/src/git.ts

@@ -597,6 +597,10 @@ export function parseGitmodules(raw: string): Submodule[] {
 	return result;
 }
 
+export interface DiffOptions {
+	cached?: boolean;
+}
+
 export class Repository {
 
 	constructor(
@@ -735,6 +739,19 @@ export class Repository {
 		}
 	}
 
+	async diff(path: string, options: DiffOptions = {}): Promise<string> {
+		const args = ['diff'];
+
+		if (options.cached) {
+			args.push('--cached');
+		}
+
+		args.push('--', path);
+
+		const result = await this.run(args);
+		return result.stdout;
+	}
+
 	async add(paths: string[]): Promise<void> {
 		const args = ['add', '-A', '--'];