PolyGerrit: Add support for suggesting branches in cherry-pick dialog

Mimics gwtui and makes it easier if you type a letter in, it should
give you the results.

Change-Id: I46a1192a565351389895599f1b1589bbb9e3d338

polygerrit-ui/app/elements/change/gr-change-actions/gr-change-actions.html

@@ -122,6 +122,7 @@ limitations under the License.
           commit-num="[[commitNum]]"
           on-confirm="_handleCherrypickConfirm"
           on-cancel="_handleConfirmDialogCancel"
+          project="[[change.project]]"
           hidden></gr-confirm-cherrypick-dialog>
       <gr-confirm-revert-dialog id="confirmRevertDialog"
           class="confirmDialog"

polygerrit-ui/app/elements/change/gr-confirm-cherrypick-dialog/gr-confirm-cherrypick-dialog.html

@@ -16,8 +16,10 @@ limitations under the License.
 
 <link rel="import" href="../../../bower_components/iron-autogrow-textarea/iron-autogrow-textarea.html">
 <link rel="import" href="../../../bower_components/polymer/polymer.html">
-<link rel="import" href="../../shared/gr-confirm-dialog/gr-confirm-dialog.html">
 <link rel="import" href="../../../styles/shared-styles.html">
+<link rel="import" href="../../shared/gr-autocomplete/gr-autocomplete.html">
+<link rel="import" href="../../shared/gr-confirm-dialog/gr-confirm-dialog.html">
+<link rel="import" href="../../shared/gr-rest-api-interface/gr-rest-api-interface.html">
 
 <dom-module id="gr-confirm-cherrypick-dialog">
   <template>
@@ -61,11 +63,12 @@ limitations under the License.
         <label for="branchInput">
           Cherry Pick to branch
         </label>
-        <input is="iron-input"
+        <gr-autocomplete
-            type="text"
             id="branchInput"
-            bind-value="{{branch}}"
+            text="{{branch}}"
+            query="[[_query]]"
             placeholder="Destination branch">
+        </gr-autocomplete>
         <label for="messageInput">
           Cherry Pick Commit Message
         </label>
@@ -78,6 +81,7 @@ limitations under the License.
             bind-value="{{message}}"></iron-autogrow-textarea>
       </div>
     </gr-confirm-dialog>
+    <gr-rest-api-interface id="restAPI"></gr-rest-api-interface>
   </template>
   <script src="gr-confirm-cherrypick-dialog.js"></script>
 </dom-module>

polygerrit-ui/app/elements/change/gr-confirm-cherrypick-dialog/gr-confirm-cherrypick-dialog.js

@@ -14,6 +14,8 @@
 (function() {
   'use strict';
 
+  const SUGGESTIONS_LIMIT = 15;
+
   Polymer({
     is: 'gr-confirm-cherrypick-dialog',
 
@@ -35,6 +37,13 @@
       commitMessage: String,
       commitNum: String,
       message: String,
+      project: String,
+      _query: {
+        type: Function,
+        value() {
+          return this._getProjectBranchesSuggestions.bind(this);
+        },
+      },
     },
 
     observers: [
@@ -59,5 +68,28 @@
       e.preventDefault();
       this.fire('cancel', null, {bubbles: false});
     },
+
+    _getProjectBranchesSuggestions(input) {
+      if (input.startsWith('refs/heads/')) {
+        input = input.substring('refs/heads/'.length);
+      }
+      return this.$.restAPI.getProjectBranches(
+          input, this.project, SUGGESTIONS_LIMIT).then(response => {
+            const branches = [];
+            let branch;
+            for (const key in response) {
+              if (!response.hasOwnProperty(key)) { continue; }
+              if (response[key].ref.startsWith('refs/heads/')) {
+                branch = response[key].ref.substring('refs/heads/'.length);
+              } else {
+                branch = response[key].ref;
+              }
+              branches.push({
+                name: branch,
+              });
+            }
+            return branches;
+          });
+    },
   });
 })();

polygerrit-ui/app/elements/change/gr-confirm-cherrypick-dialog/gr-confirm-cherrypick-dialog_test.html

@@ -36,7 +36,23 @@ limitations under the License.
     let element;
 
     setup(() => {
+      stub('gr-rest-api-interface', {
+        getProjectBranches(input) {
+          if (input.startsWith('test')) {
+            return Promise.resolve([
+              {
+                ref: 'refs/heads/test-branch',
+                revision: '67ebf73496383c6777035e374d2d664009e2aa5c',
+                can_delete: true,
+              },
+            ]);
+          } else {
+            return Promise.resolve({});
+          }
+        },
+      });
       element = fixture('basic');
+      element.project = 'test-project';
     });
 
     test('with merged change', () => {
@@ -69,5 +85,20 @@ limitations under the License.
       flushAsynchronousOperations();
       assert.equal(element.message, myNewMessage);
     });
+
+    test('_getProjectBranchesSuggestions empty', done => {
+      element._getProjectBranchesSuggestions('nonexistent').then(branches => {
+        assert.equal(branches.length, 0);
+        done();
+      });
+    });
+
+    test('_getProjectBranchesSuggestions non-empty', done => {
+      element._getProjectBranchesSuggestions('test-branch').then(branches => {
+        assert.equal(branches.length, 1);
+        assert.equal(branches[0].name, 'test-branch');
+        done();
+      });
+    });
   });
 </script>