src/vs/workbench/services/workingCopy/common/workingCopyBackupService.ts/WorkingCopyBackupsModel/has
class WorkingCopyBackupsModel:	has(resource: URI, versionId?: number, meta?: IWorkingCopyBackupMeta): boolean {
		const entry = this.cache.get(resource);
		if (!entry) {
			return false; // unknown resource
		}

		if (typeof versionId === 'number' && versionId !== entry.versionId) {
			return false; // different versionId
		}

		if (meta && !equals(meta, entry.meta)) {
			return false; // different metadata
		}

		return true;
	}