Show different controls on project member page depending on if the membership lock is in place.

app/helpers/projects_helper.rb

@@ -279,4 +279,12 @@ module ProjectsHelper
     result.password = '*****' if result.password.present?
     result
   end
+
+  def membership_locked?
+    if @project.group && @project.group.membership_lock
+      true
+    else
+      false
+    end
+  end
 end

app/views/projects/team_members/_team_member.html.haml

 - user = member.user
 %li{id: dom_id(user), class: "team_member_row access-#{member.human_access.downcase}"}
-  .pull-right
-    - if current_user_can_admin_project
-      - unless @project.personal? && user == current_user
-        .pull-left
-          = form_for(member, as: :project_member, url: project_team_member_path(@project, member.user)) do |f|
-            = f.select :access_level, options_for_select(ProjectMember.access_roles, member.access_level), {}, class: "trigger-submit"
-           
-        = link_to project_team_member_path(@project, user), data: { confirm: remove_from_project_team_message(@project, user)}, method: :delete, class: "btn-tiny btn btn-remove", title: 'Remove user from team' do
-          %i.fa.fa-minus.fa-inverse
+  - unless membership_locked?
+    .pull-right
+      - if current_user_can_admin_project
+        - unless @project.personal? && user == current_user
+          .pull-left
+            = form_for(member, as: :project_member, url: project_team_member_path(@project, member.user)) do |f|
+              = f.select :access_level, options_for_select(ProjectMember.access_roles, member.access_level), {}, class: "trigger-submit"
+             
+          = link_to project_team_member_path(@project, user), data: { confirm: remove_from_project_team_message(@project, user)}, method: :delete, class: "btn-tiny btn btn-remove", title: 'Remove user from team' do
+            %i.fa.fa-minus.fa-inverse
   = image_tag avatar_icon(user.email, 32), class: "avatar s32"
   %p
     %strong= user.name

app/views/projects/team_members/index.html.haml

 %h3.page-title
   Users with access to this project
 
-  - if can? current_user, :admin_team_member, @project
-    %span.pull-right
-      = link_to new_project_team_member_path(@project), class: "btn btn-new btn-grouped", title: "New project member" do
-        New project member
-      = link_to import_project_team_members_path(@project), class: "btn btn-grouped", title: "Import members from another project" do
-        Import members
+  - unless membership_locked?
+    - if can?(current_user, :admin_team_member, @project)
+      %span.pull-right
+        = link_to new_project_team_member_path(@project), class: "btn btn-new btn-grouped", title: "New project member" do
+          New project member
+        = link_to import_project_team_members_path(@project), class: "btn btn-grouped", title: "Import members from another project" do
+          Import members
+
 
 %p.light
   Read more about project permissions
   %strong= link_to "here", help_page_path("permissions", "permissions"), class: "vlink"
+  - if membership_locked?
+    %span.pull-right
+      Adding new user to membership is disabled by a group setting
+
 = render "team", members: @project_members
 - if @group
   = render "group_members"

app/views/shared/_group_form.html.haml

@@ -10,3 +10,10 @@
   .col-sm-10
     = f.text_area :description, maxlength: 250,
         class: 'form-control js-gfm-input', rows: 4
+.form-group
+  = f.label :name, class: 'control-label' do
+    Member lock
+  .col-sm-10
+    .checkbox
+      = f.check_box :membership_lock
+      %span.descr Prevent adding new members to project membership within this group