Created a static 'history' for importing with import {history} from 'react-router/lib/HashHistory'

this is an implementation for what @ryanflorence said on #1339 and @mjackson on #1426.

Author: Schniz

modules/BrowserHistory.js

@@ -2,6 +2,8 @@ import DOMHistory from './DOMHistory';
 import { getWindowPath, supportsHistory } from './DOMUtils';
 import NavigationTypes from './NavigationTypes';
 
+var instance = null;
+
 function updateCurrentState(extraState) {
   var state = window.history.state;
 
@@ -106,6 +108,10 @@ class BrowserHistory extends DOMHistory {
     }
   }
 
+  static history() {
+    instance = instance || new BrowserHistory();
+    return instance;
+  }
 }
 
 export default BrowserHistory;

modules/DOMHistory.js

@@ -5,7 +5,6 @@ import { getWindowScrollPosition } from './DOMUtils';
  * A history interface that assumes a DOM environment.
  */
 class DOMHistory extends History {
-
   constructor(options={}) {
     super(options);
     this.getScrollPosition = options.getScrollPosition || getWindowScrollPosition;

modules/HashHistory.js

@@ -4,6 +4,7 @@ import NavigationTypes from './NavigationTypes';
 import { getHashPath, replaceHashPath } from './DOMUtils';
 import { isAbsolutePath } from './URLUtils';
 
+var instance = null;
 var DefaultQueryKey = '_qk';
 
 function ensureSlash() {
@@ -34,7 +35,7 @@ function saveState(path, queryKey, state) {
 function readState(path, queryKey) {
   var sessionKey = getQueryStringValueFromPath(path, queryKey);
   var json = sessionKey && window.sessionStorage.getItem(sessionKey);
-  
+
   if (json) {
     try {
       return JSON.parse(json);
@@ -168,6 +169,10 @@ class HashHistory extends DOMHistory {
     return '#' + path;
   }
 
+  static history() {
+    instance = instance || new HashHistory();
+    return instance;
+  }
 }
 
 export default HashHistory;

modules/__tests__/BrowserHistory-test.js

@@ -1,6 +1,7 @@
 import describeHistory from './describeHistory';
-import BrowserHistory from '../BrowserHistory';
+import BrowserHistory, { history } from '../BrowserHistory';
 
 describe('BrowserHistory', function () {
   describeHistory(new BrowserHistory);
+  describeHistory(history());
 });

modules/__tests__/HashHistory-test.js

@@ -1,6 +1,7 @@
 import describeHistory from './describeHistory';
-import HashHistory from '../HashHistory';
+import HashHistory, { history } from '../HashHistory';
 
 describe('HashHistory', function () {
   describeHistory(new HashHistory);
+  describeHistory(history());
 });

modules/__tests__/MemoryHistory-test.js

@@ -40,7 +40,7 @@ describe('MemoryHistory', function () {
     it('cannot go forward', function () {
       expect(history.canGoForward()).toBe(false);
     });
- 
+
     describe('and then replacing that path', function () {
       beforeEach(function () {
         history.replaceState(null, '/replace');