src/vs/workbench/services/workingCopy/common/workingCopyBackupService.ts/InMemoryWorkingCopyBackupService/hasBackupSync
class InMemoryWorkingCopyBackupService:	hasBackupSync(identifier: IWorkingCopyIdentifier, versionId?: number): boolean {
		const backupResource = this.toBackupResource(identifier);

		return this.backups.has(backupResource);
	}