Updated label links to work correctly for filtering

See !3846#note_5033951

app/assets/javascripts/labels_select.js.coffee

@@ -30,7 +30,7 @@ class @LabelsSelect
       if issueUpdateURL
         labelHTMLTemplate = _.template(
             '<% _.each(labels, function(label){ %>
-            <a href="<%= ["",issueURLSplit[1], issueURLSplit[2],""].join("/") %>issues?label_name=<%= _.escape(label.title) %>">
+            <a href="<%= ["",issueURLSplit[1], issueURLSplit[2],""].join("/") %>issues?label_name[]=<%= _.escape(label.title) %>">
             <span class="label has-tooltip color-label" title="<%= _.escape(label.description) %>" style="background-color: <%= label.color %>; color: <%= label.text_color %>;">
             <%= _.escape(label.title) %>
             </span>

app/helpers/labels_helper.rb

@@ -37,7 +37,7 @@ module LabelsHelper
     link = send("namespace_project_#{type.to_s.pluralize}_path",
                 project.namespace,
                 project,
-                label_name: label.name)
+                label_name: [label.name])
 
     if block_given?
       link_to link, &block

spec/helpers/labels_helper_spec.rb

@@ -11,13 +11,13 @@ describe LabelsHelper do
       end
 
       it 'uses the instance variable' do
-        expect(link_to_label(label)).to match %r{<a href="/#{@project.to_reference}/issues\?label_name=#{label.name}"><span class="[\w\s\-]*has-tooltip".*</span></a>}
+        expect(link_to_label(label)).to match %r{<a href="/#{@project.to_reference}/issues\?label_name%5B%5D=#{label.name}"><span class="[\w\s\-]*has-tooltip".*</span></a>}
       end
     end
 
     context 'without @project set' do
       it "uses the label's project" do
-        expect(link_to_label(label)).to match %r{<a href="/#{label.project.to_reference}/issues\?label_name=#{label.name}">.*</a>}
+        expect(link_to_label(label)).to match %r{<a href="/#{label.project.to_reference}/issues\?label_name%5B%5D=#{label.name}">.*</a>}
       end
     end
 
@@ -25,7 +25,7 @@ describe LabelsHelper do
       let(:another_project) { double('project', namespace: 'foo3', to_param: 'bar3') }
 
       it 'links to merge requests page' do
-        expect(link_to_label(label, project: another_project)).to match %r{<a href="/foo3/bar3/issues\?label_name=#{label.name}">.*</a>}
+        expect(link_to_label(label, project: another_project)).to match %r{<a href="/foo3/bar3/issues\?label_name%5B%5D=#{label.name}">.*</a>}
       end
     end
 
@@ -33,7 +33,7 @@ describe LabelsHelper do
       ['issue', :issue, 'merge_request', :merge_request].each do |type|
         context "set to #{type}" do
           it 'links to correct page' do
-            expect(link_to_label(label, type: type)).to match %r{<a href="/#{label.project.to_reference}/#{type.to_s.pluralize}\?label_name=#{label.name}">.*</a>}
+            expect(link_to_label(label, type: type)).to match %r{<a href="/#{label.project.to_reference}/#{type.to_s.pluralize}\?label_name%5B%5D=#{label.name}">.*</a>}
           end
         end
       end