Show a custom WIP help message for MR's with WIP commits

app/views/projects/merge_requests/_new_submit.html.haml

@@ -11,7 +11,7 @@
     = link_to 'Change branches', mr_change_branches_path(@merge_request)
 %hr
 = form_for [@project.namespace.becomes(Namespace), @project, @merge_request], html: { class: 'merge-request-form form-horizontal common-note-form js-requires-input js-quick-submit' } do |f|
-  = render 'shared/issuable/form', f: f, issuable: @merge_request
+  = render 'shared/issuable/form', f: f, issuable: @merge_request, commits: @commits
   = f.hidden_field :source_project_id
   = f.hidden_field :source_branch
   = f.hidden_field :target_project_id

app/views/shared/issuable/_form.html.haml

 - form = local_assigns.fetch(:f)
+- commits = local_assigns[:commits]
 - project = @target_project || @project
 
 = form_errors(issuable)
@@ -14,7 +15,7 @@
   = form.label :title, class: 'control-label'
 
   = render 'shared/issuable/form/template_selector', issuable: issuable
-  = render 'shared/issuable/form/title', issuable: issuable, form: form
+  = render 'shared/issuable/form/title', issuable: issuable, form: form, has_wip_commits: commits && commits.detect(&:work_in_progress?)
 
 = render 'shared/issuable/form/description', issuable: issuable, form: form
 

app/views/shared/issuable/form/_title.html.haml

 - issuable = local_assigns.fetch(:issuable)
+- has_wip_commits = local_assigns.fetch(:has_wip_commits)
 - form = local_assigns.fetch(:form)
 - no_issuable_templates = issuable_templates(issuable).empty?
 - div_class = no_issuable_templates ? 'col-sm-10' : 'col-sm-7 col-lg-8'
@@ -18,6 +19,9 @@
         %strong Work In Progress
         merge request to be merged when it's ready.
       .js-no-wip-explanation
+        - if has_wip_commits
+          It looks like you have some WIP commits in this branch.
+          %br
         %a.js-toggle-wip{ href: '', tabindex: -1 }
           Start the title with
           %code WIP:

spec/features/merge_requests/wip_message_spec.rb

+require 'spec_helper'
+
+feature 'Work In Progress help message', feature: true do
+  let!(:project) { create(:project, visibility_level: Gitlab::VisibilityLevel::PUBLIC) }
+  let!(:user)    { create(:user) }
+
+  before do
+    project.team << [user, :master]
+    login_as(user)
+  end
+
+  context 'with WIP commits' do
+    it 'shows a specific WIP hint' do
+      visit new_namespace_project_merge_request_path(
+        project.namespace,
+        project,
+        merge_request: {
+          source_project_id: project.id,
+          target_project_id: project.id,
+          source_branch: 'wip',
+          target_branch: 'master'
+        }
+      )
+
+      within_wip_explanation do
+        expect(page).to have_text(
+          'It looks like you have some WIP commits in this branch'
+        )
+      end
+    end
+  end
+
+  context 'without WIP commits' do
+    it 'shows the regular WIP message' do
+      visit new_namespace_project_merge_request_path(
+        project.namespace,
+        project,
+        merge_request: {
+          source_project_id: project.id,
+          target_project_id: project.id,
+          source_branch: 'fix',
+          target_branch: 'master'
+        }
+      )
+
+      within_wip_explanation do
+        expect(page).not_to have_text(
+          'It looks like you have some WIP commits in this branch'
+        )
+        expect(page).to have_text(
+          "Start the title with WIP: to prevent a Work In Progress merge \
+request from being merged before it's ready"
+        )
+      end
+    end
+  end
+
+  def within_wip_explanation(&block)
+    page.within '.js-no-wip-explanation' do
+      yield
+    end
+  end
+end