src/vs/workbench/contrib/search/common/searchModel.ts/FolderMatch/onFileChange
class FolderMatch:	private onFileChange(fileMatch: FileMatch, removed = false): void {
		let added = false;
		if (!this._fileMatches.has(fileMatch.resource)) {
			this.doAdd(fileMatch);
			added = true;
		}
		if (fileMatch.count() === 0) {
			this.doRemove(fileMatch, false, false);
			added = false;
			removed = true;
		}
		if (!this._replacingAll) {
			this._onChange.fire({ elements: [fileMatch], added: added, removed: removed });
		}
	}