AngularJS: add selected dropdown item to dropdown toggle - angularjs

Question

How can I add the selected item from dropdown menu to the button that opens that dropdown?
Example: I want to replace 'DIFFERENCES' with text selected from the dropdown menu; if I select 'All' then the text 'DIFFERENCES' should be replaced with 'All'...
<div class="filter-requests btn-group">
<div data-toggle="dropdown">
<a href="#" class="btn btn-default dropdown-toggle">
DIFFERENCES
<i class="fa fa-chevron-down"></i>
</a>
</div>
<ul class="dropdown-menu">
<li>All</li>
<li><a href="#" >Exclusions</a></li>
<li><a href="#" >Differences</a></li>
<li><a href="#" >Variable Differences</a></li>
<li><a href="#" >Path Differences</a></li>
</ul>
</div>

Answer 1

view.html
<div class="btn-group" uib-dropdown is-open="status.isopen">
<button id="single-button" type="button" class="btn btn-primary" uib-dropdown-toggle>
{{selected || 'Select one'}} <span class="caret"></span>
</button>
<ul class="dropdown-menu" uib-dropdown-menu role="menu" aria-labelledby="single-button">
<li role="menuitem">Action</li>
<li role="menuitem">Another action</li>
<li role="menuitem">Something else here</li>
<li class="divider"></li>
<li role="menuitem">Separated link</li>
</ul>
</div>
controller.js
$scope.selected = null;
$scope.changeOption = function(text) {
$scope.selected = text;
}

Answer 2

try like this.
var app = angular.module("app",[]);
app.controller("ctrl" , function($scope){
$scope.row = "";
$scope.items = ['All','Exclusions','Differences','Variable Differences'];
$scope.selectRow = function(item){
$scope.row = item;
}
});
<script src="https://ajax.googleapis.com/ajax/libs/angularjs/1.2.23/angular.min.js"></script>
<div ng-app="app" ng-controller="ctrl" class="filter-requests btn-group">
<div data-toggle="dropdown">
<a href="#" class="btn btn-default dropdown-toggle">
{{row}}
<i class="fa fa-chevron-down"></i>
</a>
</div>
<ul class="dropdown-menu" >
<li ng-repeat="item in items" ng-click="selectRow(item)">
{{item}}
</li>
</ul>
</div>