Don't ask the user to "merge this request manually".

1. If they are a developer with "Developers can Merge" switched on.

app/models/merge_request.rb

@@ -556,6 +556,11 @@ class MergeRequest < ActiveRecord::Base
     access.can_push_to_branch?(target_branch) || access.can_merge_to_branch?(target_branch)
   end
+  def can_be_merged_via_command_line_by?(user)
+    access = ::Gitlab::UserAccess.new(user, project: project)
+    access.can_push_to_branch?(target_branch)
+  end
+
   def mergeable_ci_state?
     return true unless project.only_allow_merge_if_build_succeeds?

app/views/projects/merge_requests/widget/open/_conflicts.html.haml

@@ -4,7 +4,7 @@
 %p
   Please resolve these conflicts or
-  - if @merge_request.can_be_merged_by?(current_user)
+  - if @merge_request.can_be_merged_via_command_line_by?(current_user)
     #{link_to "merge this request manually", "#modal_merge_info", class: "how_to_merge_link vlink", "data-toggle" => "modal"}.
   - else
     ask someone with write access to this repository to merge this request manually.