fix($state.go): param inheritance shouldn't inherit from siblings

Due to a bug in the ancestors() function, we were treating any states at the same depth from root as "ancestors". This means siblings were inheriting parameters from each other. Interestingly ui-sref generated the correct links, but the click handler then broke the link.

Unfortunately this is a breaking change if someone depends on the broken behavior of inheriting all the params on sibling state transitions. The fix for these folks is mostly simple: create a common parent state that contains parameters that need to be shared. Unfortunately it can introduce quite a bit of churn in the codebase.

src/common.js

@@ -37,8 +37,7 @@ function ancestors(first, second) {
   var path = [];
 
   for (var n in first.path) {
-    if (first.path[n] === "") continue;
-    if (!second.path[n]) break;
+    if (first.path[n] !== second.path[n]) break;
     path.push(first.path[n]);
   }
   return path;

test/stateSpec.js

@@ -93,7 +93,13 @@ describe('state', function () {
       })
 
       .state('first', { url: '^/first/subpath' })
-      .state('second', { url: '^/second' });
+      .state('second', { url: '^/second' })
+
+      // State param inheritance tests. param1 is inherited by sub1 & sub2;
+      // param2 should not be transferred (unless explicitly set).
+      .state('root', { url: '^/root?param1' })
+      .state('root.sub1', {url: '/1?param2' })
+      .state('root.sub2', {url: '/2?param2' });
 
     $provide.value('AppInjectable', AppInjectable);
   }));
@@ -669,6 +675,9 @@ describe('state', function () {
         'home.redirect',
         'resolveFail',
         'resolveTimeout',
+        'root',
+        'root.sub1',
+        'root.sub2',
         'second'
       ];
       expect(list.map(function(state) { return state.name; })).toEqual(names);
@@ -802,6 +811,29 @@ describe('state', function () {
     }));
   });
 
+  describe('substate and stateParams inheritance', function() {
+    it('should inherit the parent param', inject(function ($state, $stateParams, $q) {
+      initStateTo($state.get('root'), {param1: 1});
+      $state.go('root.sub1', {param2: 2});
+      $q.flush();
+      expect($state.current.name).toEqual('root.sub1');
+      expect($stateParams).toEqual({param1: '1', param2: '2'});
+    }));
+
+    it('should not inherit siblings\' states', inject(function ($state, $stateParams, $q) {
+      initStateTo($state.get('root'), {param1: 1});
+      $state.go('root.sub1', {param2: 2});
+      $q.flush();
+      expect($state.current.name).toEqual('root.sub1');
+
+      $state.go('root.sub2');
+      $q.flush();
+      expect($state.current.name).toEqual('root.sub2');
+
+      expect($stateParams).toEqual({param1: '1', param2: null});
+    }));
+  });
+
   describe('html5Mode compatibility', function() {
 
     it('should generate non-hashbang URLs in HTML5 mode', inject(function ($state) {