Unescape branch names in compare commit

Closes #1399
Closes https://github.com/gitlabhq/gitlabhq/issues/9105

CHANGELOG

@@ -21,6 +21,8 @@ v 7.11.0 (unreleased)
   - Add default project and snippet visibility settings to the admin web UI.
   -
   - Fix bug where commit data would not appear in some subdirectories (Stan Hu)
+  - Unescape branch names in compare commit (Stan Hu)
+  -
   - Fix bug where Slack service channel was not saved in admin template settings. (Stan Hu)
   - Move snippets UI to fluid layout
   - Improve UI for sidebar. Increase separation between navigation and content

app/controllers/projects/compare_controller.rb

+require 'addressable/uri'
+
 class Projects::CompareController < Projects::ApplicationController
   # Authorize
   before_action :require_non_empty_project
@@ -7,8 +9,8 @@ class Projects::CompareController < Projects::ApplicationController
   end
 
   def show
-    base_ref = params[:from]
-    head_ref = params[:to]
+    base_ref = Addressable::URI.unescape(params[:from])
+    head_ref = Addressable::URI.unescape(params[:to])
 
     compare_result = CompareService.new.execute(
       current_user,

spec/controllers/projects/compare_controller_spec.rb

+require 'spec_helper'
+
+describe Projects::CompareController do
+  let(:project) { create(:project) }
+  let(:user) { create(:user) }
+  let(:ref_from) { "improve%2Fawesome" }
+  let(:ref_to) { "feature" }
+
+  before do
+    sign_in(user)
+    project.team << [user, :master]
+  end
+
+  it 'compare should show some diffs' do
+    get(:show, namespace_id: project.namespace.to_param,
+        project_id: project.to_param, from: ref_from, to: ref_to)
+
+    expect(response).to be_success
+    expect(assigns(:diffs).length).to be >= 1
+    expect(assigns(:commits).length).to be >= 1
+  end
+end