src/vs/workbench/services/workingCopy/common/workingCopyBackupService.ts/WorkingCopyBackupsModel/add
class WorkingCopyBackupsModel:	add(resource: URI, versionId = 0, meta?: IWorkingCopyBackupMeta): void {
		this.cache.set(resource, {
			versionId,
			meta: deepClone(meta)
		});
	}