This is an old patch for redmine to create subgroups feature, not works in recent redmine's

patch subgroups redmine

diff --git a/app/controllers/groups_controller.rb b/app/controllers/groups_controller.rb
index db56eff..06f9284 100644
--- a/app/controllers/groups_controller.rb
+++ b/app/controllers/groups_controller.rb
@@ -106,33 +106,33 @@ class GroupsController < ApplicationController
     end
   end
   
-  def add_users
+  def add_principals
     @group = Group.find(params[:id])
-    users = User.find_all_by_id(params[:user_ids])
-    @group.users << users if request.post?
+    principals = Principal.find_all_by_id(params[:user_ids]) - @group.parent_groups
+    @group.principals << principals if request.post?
     respond_to do |format|
       format.html { redirect_to :controller => 'groups', :action => 'edit', :id => @group, :tab => 'users' }
       format.js { 
         render(:update) {|page| 
           page.replace_html "tab-content-users", :partial => 'groups/users'
-          users.each {|user| page.visual_effect(:highlight, "user-#{user.id}") }
+          principals.each {|principal| page.visual_effect(:highlight, "user-#{principal.id}") }
         }
       }
     end
   end
   
-  def remove_user
+  def remove_principal
     @group = Group.find(params[:id])
-    @group.users.delete(User.find(params[:user_id])) if request.post?
+    @group.principals.delete(Principal.find(params[:user_id])) if request.post?
     respond_to do |format|
       format.html { redirect_to :controller => 'groups', :action => 'edit', :id => @group, :tab => 'users' }
       format.js { render(:update) {|page| page.replace_html "tab-content-users", :partial => 'groups/users'} }
     end
   end
   
-  def autocomplete_for_user
+  def autocomplete_for_principal
     @group = Group.find(params[:id])
-    @users = User.active.not_in_group(@group).like(params[:q]).all(:limit => 100)
+    @principals = Principal.active.not_in_group(@group).like(params[:q]).all(:limit => 100) - @group.parent_groups
     render :layout => false
   end
   
diff --git a/app/models/group.rb b/app/models/group.rb
index 1b55c25..1817eb2 100644
--- a/app/models/group.rb
+++ b/app/models/group.rb
@@ -16,20 +16,25 @@
 # Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA  02110-1301, USA.
 
 class Group < Principal
-  has_and_belongs_to_many :users, :after_add => :user_added,
-                                  :after_remove => :user_removed
+  has_and_belongs_to_many :principals, :after_add => :principal_added,
+                                       :after_remove => :principal_removed
   
   acts_as_customizable
   
   validates_presence_of :lastname
   validates_uniqueness_of :lastname, :case_sensitive => false
   validates_length_of :lastname, :maximum => 30
-    
+
+  named_scope :direct_parents, lambda {|group|
+    group_id = group.is_a?(Group) ? group.id : group.to_i
+    { :conditions => ["#{Group.table_name}.id IN (SELECT gp.group_id FROM #{table_name_prefix}groups_principals#{table_name_suffix} gp WHERE gp.principal_id = ?)", group_id] }
+  }
+
   def to_s
     lastname.to_s
   end
   
-  def user_added(user)
+  def principal_added(user)
     members.each do |member|
       next if member.project.nil?
       user_member = Member.find_by_project_id_and_user_id(member.project_id, user.id) || Member.new(:project_id => member.project_id, :user_id => user.id)
@@ -40,10 +45,19 @@ class Group < Principal
     end
   end
   
-  def user_removed(user)
+  def principal_removed(user)
     members.each do |member|
       MemberRole.find(:all, :include => :member,
                             :conditions => ["#{Member.table_name}.user_id = ? AND #{MemberRole.table_name}.inherited_from IN (?)", user.id, member.member_role_ids]).each(&:destroy)
     end
   end
+
+  def parent_groups
+    direct_parents = Group.direct_parents(self).all
+    parent_groups = direct_parents
+    direct_parents.each do |direct_parent|
+      parent_groups += direct_parent.parent_groups
+    end
+    return parent_groups
+  end
 end
diff --git a/app/models/member_role.rb b/app/models/member_role.rb
index 9c28d41..7ab4eed 100644
--- a/app/models/member_role.rb
+++ b/app/models/member_role.rb
@@ -44,8 +44,8 @@ class MemberRole < ActiveRecord::Base
   
   def add_role_to_group_users
     if member.principal.is_a?(Group)
-      member.principal.users.each do |user|
-        user_member = Member.find_by_project_id_and_user_id(member.project_id, user.id) || Member.new(:project_id => member.project_id, :user_id => user.id)
+      member.principal.principals.each do |principal|
+        user_member = Member.find_by_project_id_and_user_id(member.project_id, principal.id) || Member.new(:project_id => member.project_id, :user_id => principal.id)
         user_member.member_roles << MemberRole.new(:role => role, :inherited_from => id)
         user_member.save!
       end
diff --git a/app/models/principal.rb b/app/models/principal.rb
index b3e07dd..cfd4021 100644
--- a/app/models/principal.rb
+++ b/app/models/principal.rb
@@ -21,6 +21,8 @@ class Principal < ActiveRecord::Base
   has_many :members, :foreign_key => 'user_id', :dependent => :destroy
   has_many :memberships, :class_name => 'Member', :foreign_key => 'user_id', :include => [ :project, :roles ], :conditions => "#{Project.table_name}.status=#{Project::STATUS_ACTIVE}", :order => "#{Project.table_name}.name"
   has_many :projects, :through => :memberships
+  has_and_belongs_to_many :groups, :after_add => Proc.new {|principal, group| group.principal_added(principal)},
+                                   :after_remove => Proc.new {|principal, group| group.principal_removed(principal)}
 
   # Groups and active users
   named_scope :active, :conditions => "#{Principal.table_name}.type='Group' OR (#{Principal.table_name}.type='User' AND #{Principal.table_name}.status = 1)"
@@ -46,6 +48,15 @@ class Principal < ActiveRecord::Base
       principal.class.name <=> self.class.name
     end
   end
+
+  named_scope :in_group, lambda {|group|
+    group_id = group.is_a?(Group) ? group.id : group.to_i
+    { :conditions => ["#{Principal.table_name}.id IN (SELECT gu.principal_id FROM #{table_name_prefix}groups_principals#{table_name_suffix} gu WHERE gu.group_id = ?)", group_id] }
+  }
+  named_scope :not_in_group, lambda {|group|
+    group_id = group.is_a?(Group) ? group.id : group.to_i
+    { :conditions => ["#{Principal.table_name}.id NOT IN (SELECT gu.principal_id FROM #{table_name_prefix}groups_principals#{table_name_suffix} gu WHERE gu.group_id = ?) AND #{Principal.table_name}.id <> ?", group_id, group_id] }
+  }
   
   protected
   
diff --git a/app/models/user.rb b/app/models/user.rb
index c06a907..7099ce8 100644
--- a/app/models/user.rb
+++ b/app/models/user.rb
@@ -43,8 +43,6 @@ class User < Principal
     ['none', :label_user_mail_option_none]
   ]
 
-  has_and_belongs_to_many :groups, :after_add => Proc.new {|user, group| group.user_added(user)},
-                                   :after_remove => Proc.new {|user, group| group.user_removed(user)}
   has_many :issue_categories, :foreign_key => 'assigned_to_id', :dependent => :nullify
   has_many :changesets, :dependent => :nullify
   has_one :preference, :dependent => :destroy, :class_name => 'UserPreference'
@@ -76,15 +74,6 @@ class User < Principal
 
   before_destroy :remove_references_before_destroy
   
-  named_scope :in_group, lambda {|group|
-    group_id = group.is_a?(Group) ? group.id : group.to_i
-    { :conditions => ["#{User.table_name}.id IN (SELECT gu.user_id FROM #{table_name_prefix}groups_users#{table_name_suffix} gu WHERE gu.group_id = ?)", group_id] }
-  }
-  named_scope :not_in_group, lambda {|group|
-    group_id = group.is_a?(Group) ? group.id : group.to_i
-    { :conditions => ["#{User.table_name}.id NOT IN (SELECT gu.user_id FROM #{table_name_prefix}groups_users#{table_name_suffix} gu WHERE gu.group_id = ?)", group_id] }
-  }
-  
   def before_create
     self.mail_notification = Setting.default_notification_option if self.mail_notification.blank?
     true
diff --git a/app/views/groups/_users.html.erb b/app/views/groups/_users.html.erb
index d7c462e..88538a5 100644
--- a/app/views/groups/_users.html.erb
+++ b/app/views/groups/_users.html.erb
@@ -1,16 +1,16 @@
 <div class="splitcontentleft">
-<% if @group.users.any? %>
+<% if @group.principals.any? %>
 	<table class="list users">
 		<thead><tr>
-		  <th><%= l(:label_user) %></th>
+		  <th><%= l(:label_user) %> / <%= l(:label_group) %></th>
 		  <th style="width:15%"></th>
 		</tr></thead>
 		<tbody>
-		<% @group.users.sort.each do |user| %>
+		<% @group.principals.sort.each do |user| %>
 			<tr id="user-<%= user.id %>" class="<%= cycle 'odd', 'even' %>">
 				<td class="user"><%= link_to_user user %></td>
 			  <td class="buttons">
-			      <%= link_to_remote l(:button_delete), { :url => { :controller => 'groups', :action => 'remove_user', :id => @group, :user_id => user },
+			      <%= link_to_remote l(:button_delete), { :url => { :controller => 'groups', :action => 'remove_principal', :id => @group, :user_id => user },
 			      																				:method => :post },
 			      																		  :class => 'icon icon-del' %>
 			  </td>
@@ -24,21 +24,21 @@
 </div>
 
 <div class="splitcontentright">
-<% users = User.active.not_in_group(@group).all(:limit => 100) %>
-<% if users.any? %>
-  <% remote_form_for(:group, @group, :url => {:controller => 'groups', :action => 'add_users', :id => @group}, :method => :post) do |f| %>
+<% principals = Principal.active.not_in_group(@group).all(:limit => 100) - @group.parent_groups %>
+<% if principals.any? %>
+  <% remote_form_for(:group, @group, :url => {:controller => 'groups', :action => 'add_principals', :id => @group}, :method => :post) do |f| %>
     <fieldset><legend><%=l(:label_user_new)%></legend>
     
-		<p><%= label_tag "user_search", l(:label_user_search) %><%= text_field_tag 'user_search', nil %></p>
+		<p><%= label_tag "user_search", l(:label_principal_search) %><%= text_field_tag 'user_search', nil %></p>
 		<%= observe_field(:user_search,
                  :frequency => 0.5,
-                 :update => :users,
-                 :url => { :controller => 'groups', :action => 'autocomplete_for_user', :id => @group },
+                 :update => :principals,
+                 :url => { :controller => 'groups', :action => 'autocomplete_for_principal', :id => @group },
                  :with => 'q')
                   %>
 		
-		<div id="users">
-			<%= principals_check_box_tags 'user_ids[]', users %>
+		<div id="principals">
+			<%= principals_check_box_tags 'user_ids[]', principals %>
 		</div>
    	
     <p><%= submit_tag l(:button_add) %></p>
diff --git a/app/views/groups/autocomplete_for_principal.html.erb b/app/views/groups/autocomplete_for_principal.html.erb
new file mode 100644
index 0000000..5f8163d
--- /dev/null
+++ b/app/views/groups/autocomplete_for_principal.html.erb
@@ -0,0 +1 @@
+<%= principals_check_box_tags 'user_ids[]', @principals %>
diff --git a/app/views/groups/autocomplete_for_user.html.erb b/app/views/groups/autocomplete_for_user.html.erb
deleted file mode 100644
index de1b007..0000000
--- a/app/views/groups/autocomplete_for_user.html.erb
+++ /dev/null
@@ -1 +0,0 @@
-<%= principals_check_box_tags 'user_ids[]', @users %>
diff --git a/app/views/groups/index.html.erb b/app/views/groups/index.html.erb
index 48b9ab4..2ab073e 100644
--- a/app/views/groups/index.html.erb
+++ b/app/views/groups/index.html.erb
@@ -15,7 +15,7 @@
 <% @groups.each do |group| %>
   <tr class="<%= cycle 'odd', 'even' %>">
     <td><%= link_to h(group), :action => 'edit', :id => group %></td>
-    <td align="center"><%= group.users.size %></td>
+    <td align="center"><%= group.principals.size %></td>
     <td class="buttons"><%= link_to l(:button_delete), group, :confirm => l(:text_are_you_sure), :method => :delete, :class => 'icon icon-del' %></td>
   </tr>
 <% end %>
diff --git a/app/views/groups/show.html.erb b/app/views/groups/show.html.erb
index 02927eb..3011581 100644
--- a/app/views/groups/show.html.erb
+++ b/app/views/groups/show.html.erb
@@ -1,7 +1,7 @@
 <h2><%= link_to l(:label_group_plural), groups_path %> &#187; <%=h @group %></h2>
 
 <ul>
-<% @group.users.each do |user| %>
-    <li><%=h user %></li>
+<% @group.principals.each do |principal| %>
+    <li><%=h principal %></li>
 <% end %>
 </ul>
diff --git a/db/migrate/20110428091629_refactor_group_users_as_principals.rb b/db/migrate/20110428091629_refactor_group_users_as_principals.rb
new file mode 100644
index 0000000..42f66e5
--- /dev/null
+++ b/db/migrate/20110428091629_refactor_group_users_as_principals.rb
@@ -0,0 +1,15 @@
+class RefactorGroupUsersAsPrincipals < ActiveRecord::Migration
+  def self.up
+    rename_table :groups_users, :groups_principals
+    change_table :groups_principals do |t|
+      t.rename :user_id, :principal_id
+    end
+  end
+
+  def self.down
+    rename_table :groups_principals, :groups_users
+    change_table :groups_principals do |t|
+      t.rename :principal_id, :user_id
+    end
+  end
+end

By recent versions, you mean version 3?