Merge from master

extensions/git/src/util.ts

@@ -3,8 +3,6 @@
  *  Licensed under the Source EULA. See License.txt in the project root for license information.
  *--------------------------------------------------------------------------------------------*/
 
-'use strict';
-
 import { Event } from 'vscode';
 import { dirname, sep } from 'path';
 import { Readable } from 'stream';
@@ -35,7 +33,7 @@ export function combinedDisposable(disposables: IDisposable[]): IDisposable {
 export const EmptyDisposable = toDisposable(() => null);
 
 export function fireEvent<T>(event: Event<T>): Event<T> {
-	return (listener, thisArgs = null, disposables?) => event(_ => listener.call(thisArgs), null, disposables);
+	return (listener, thisArgs = null, disposables?) => event(_ => (listener as any).call(thisArgs), null, disposables);
 }
 
 export function mapEvent<I, O>(event: Event<I>, map: (i: I) => O): Event<O> {
@@ -46,6 +44,18 @@ export function filterEvent<T>(event: Event<T>, filter: (e: T) => boolean): Even
 	return (listener, thisArgs = null, disposables?) => event(e => filter(e) && listener.call(thisArgs, e), null, disposables);
 }
 
+export function latchEvent<T>(event: Event<T>): Event<T> {
+	let firstCall = true;
+	let cache: T;
+
+	return filterEvent(event, value => {
+		let shouldEmit = firstCall || value !== cache;
+		firstCall = false;
+		cache = value;
+		return shouldEmit;
+	});
+}
+
 export function anyEvent<T>(...events: Event<T>[]): Event<T> {
 	return (listener, thisArgs = null, disposables?) => {
 		const result = combinedDisposable(events.map(event => event(i => listener.call(thisArgs, i))));
@@ -268,7 +278,7 @@ export function readBytes(stream: Readable, bytes: number): Promise<Buffer> {
 	});
 }
 
-export enum Encoding {
+export const enum Encoding {
 	UTF8 = 'utf8',
 	UTF16be = 'utf16be',
 	UTF16le = 'utf16le'