Rewrite and improve git backend logic. Fix project movind. Raise exception to prevent unexpected issues

app/models/namespace.rb

@@ -35,6 +35,10 @@ class Namespace < ActiveRecord::Base
     where("name LIKE :query OR path LIKE :query", query: "%#{query}%")
   end
 
+  def self.global_id
+    'GLN'
+  end
+
   def to_param
     path
   end
@@ -51,6 +55,9 @@ class Namespace < ActiveRecord::Base
   def move_dir
     old_path = File.join(Gitlab.config.git_base_path, path_was)
     new_path = File.join(Gitlab.config.git_base_path, path)
+    if File.exists?(new_path)
+      raise "Already exists"
+    end
     system("mv #{old_path} #{new_path}")
   end
 

app/models/project.rb

@@ -111,12 +111,14 @@ class Project < ActiveRecord::Base
 
         # Apply namespace if user has access to it
         # else fallback to user namespace
-        project.namespace_id = user.namespace_id
+        if namespace_id != Namespace.global_id
+          project.namespace_id = user.namespace_id
 
-        if namespace_id
-          group = Group.find_by_id(namespace_id)
-          if user.can? :manage_group, group
-            project.namespace_id = namespace_id
+          if namespace_id
+            group = Group.find_by_id(namespace_id)
+            if user.can? :manage_group, group
+              project.namespace_id = namespace_id
+            end
           end
         end
 
@@ -254,12 +256,16 @@ class Project < ActiveRecord::Base
       old_dir = old_namespace.try(:path) || ''
       new_dir = new_namespace.try(:path) || ''
 
-      old_repo = File.join(old_dir, self.path)
-
-      git_host.move_repository(old_repo, self.path_with_namespace, self)
+      old_repo = if old_dir.present?
+                   File.join(old_dir, self.path)
+                 else
+                   self.path
+                 end
 
       Gitlab::ProjectMover.new(self, old_dir, new_dir).execute
 
+      git_host.move_repository(old_repo, self.path_with_namespace, self)
+
       save!
     end
   end