Rename logo, apply for Slack too

app/controllers/projects/mattermosts_controller.rb

@@ -30,7 +30,7 @@ class Projects::MattermostsController < Projects::ApplicationController
   def configure_params
     params.require(:mattermost).permit(:trigger, :team_id).merge(
       url: service_trigger_url(@service),
-      icon_url: asset_url('mattermost-command-logo.png'))
+      icon_url: asset_url('slash-command-logo.png'))
   end
 
   def teams

app/views/projects/services/slack_slash_commands/_help.html.haml

@@ -50,7 +50,7 @@
     .form-group
       = label_tag nil, 'Customize icon', class: 'col-sm-2 col-xs-12 control-label'
       .col-sm-10.col-xs-12.text-block
-        = image_tag(asset_url('gitlab_logo.png'), width: 36, height: 36)
+        = image_tag(asset_url('slash-command-logo.png'), width: 36, height: 36)
         = link_to('Download image', asset_url('gitlab_logo.png'), class: 'btn btn-sm', target: '_blank')
 
     .form-group

spec/features/projects/services/mattermost_slash_command_spec.rb

@@ -49,4 +49,10 @@ feature 'Setup Mattermost slash commands', feature: true do
       end
     end
   end
+
+  describe 'stable logo url' do
+    it 'shows a publicly available logo' do
+      expect(File.exist?(Rails.root.join('public/slash-command-logo.png')))
+    end
+  end
 end