src/vs/workbench/services/environment/browser/environmentService.ts/BrowserWorkbenchEnvironmentService/filesToDiff
class BrowserWorkbenchEnvironmentService:	get filesToDiff(): IPath[] | undefined {
		if (this.payload) {
			const fileToDiffPrimary = this.payload.get('diffFilePrimary');
			const fileToDiffSecondary = this.payload.get('diffFileSecondary');
			if (fileToDiffPrimary && fileToDiffSecondary) {
				return [
					{ fileUri: URI.parse(fileToDiffSecondary) },
					{ fileUri: URI.parse(fileToDiffPrimary) }
				];
			}
		}

		return undefined;
	}