src/vs/workbench/services/workingCopy/common/workingCopyBackupService.ts/InMemoryWorkingCopyBackupService/discardBackups
class InMemoryWorkingCopyBackupService:	async discardBackups(filter?: { except: IWorkingCopyIdentifier[] }): Promise<void> {
		const except = filter?.except;
		if (Array.isArray(except) && except.length > 0) {
			const exceptMap = new ResourceMap<boolean>();
			for (const exceptWorkingCopy of except) {
				exceptMap.set(this.toBackupResource(exceptWorkingCopy), true);
			}

			for (const backup of await this.getBackups()) {
				if (!exceptMap.has(this.toBackupResource(backup))) {
					await this.discardBackup(backup);
				}
			}
		} else {
			this.backups.clear();
		}
	}