feature(repository): add getBranch

closes #372

Author: deecewan

lib/Repository.js

@@ -152,6 +152,17 @@ class Repository extends Requestable {
       return this._request('GET', `/repos/${this.__fullname}/git/blobs/${sha}`, null, cb, 'raw');
    }
 
+   /**
+    * Get a single branch
+    * @see https://developer.github.com/v3/repos/branches/#get-branch
+    * @param {string} branch - the name of the branch to fetch
+    * @param {Requestable.callback} cb - will receive the branch from the API
+    * @returns {Promise} - the promise for the http request
+    */
+   getBranch(branch, cb) {
+      return this._request('GET', `/repos/${this.__fullname}/branches/${branch}`, null, cb);
+   }
+
    /**
     * Get a commit from the repository
     * @see https://developer.github.com/v3/repos/commits/#get-a-single-commit

test/repository.spec.js

@@ -52,6 +52,14 @@ describe('Repository', function() {
          }));
       });
 
+      it('should get a branch', function(done) {
+         remoteRepo.getBranch('master', assertSuccessful(done, function(err, content) {
+            expect(content.name).to.be('master');
+
+            done();
+         }));
+      });
+
       it('should show repo contents', function(done) {
          remoteRepo.getContents('master', '', false, assertSuccessful(done, function(err, contents) {
             expect(contents).to.be.an.array();