Prepare fork to given namespace

Issue #210 (closed) reported that fork into a group's namespace is not possible thru gitlab and in the merge request "to be able to fork a project through the API", two people wanted to also be able to fork to a group's namespace.

Example user story for this from the fork merge request: "+1 For training courses we are running, we want to fork a project in a known state, rename it and then move it to a Training Group. It would be great to be able to script this."

This is the 1st of two commits to make this happen:

Add the Middleware for supporting forks to a given namespace. gitlab-shell's 2nd argument for fork is already the namespace in which the forked project shall be created. This commit makes this functionality available in the gitlab-rails layer.

app/services/projects/fork_service.rb

@@ -2,11 +2,9 @@ module Projects
class ForkService < BaseService
include Gitlab::ShellAdapter
-    def initialize(project, user)
-      @from_project, @current_user = project, user
-    end
-
def execute
+      @from_project = @project
+
project_params = {
visibility_level: @from_project.visibility_level,
description: @from_project.description,
@@ -15,8 +13,15 @@ module Projects
project = Project.new(project_params)
project.name = @from_project.name
project.path = @from_project.path
-      project.namespace = current_user.namespace
-      project.creator = current_user
+      project.namespace = @current_user.namespace
+      if namespace = @params[:namespace]
+        project.namespace = namespace
+      end
+      project.creator = @current_user
+      unless @current_user.can?(:create_projects, project.namespace)
+        project.errors.add(:namespace, 'insufficient access rights')
+        return project
+      end
# If the project cannot save, we do not want to trigger the project destroy
# as this can have the side effect of deleting a repo attached to an existing
@@ -27,7 +32,7 @@ module Projects
#First save the DB entries as they can be rolled back if the repo fork fails
project.build_forked_project_link(forked_to_project_id: project.id, forked_from_project_id: @from_project.id)
if project.save
-              project.team << [current_user, :master]
+              project.team << [@current_user, :master]
end
#Now fork the repo
unless gitlab_shell.fork_repository(@from_project.path_with_namespace, project.namespace.path)