Use the namespace validator for validating all paths

Since the namespacevalidator now knows the difference between a
top-level and another path, this could all be handled there.

app/models/project.rb

@@ -196,7 +196,7 @@ class Project < ActiveRecord::Base
               message: Gitlab::Regex.project_name_regex_message }
   validates :path,
     presence: true,
-    project_path: true,
+    namespace: true,
     length: { maximum: 255 },
     format: { with: Gitlab::Regex.project_path_regex,
               message: Gitlab::Regex.project_path_regex_message },

app/validators/project_path_validator.rb

@@ -1,27 +0,0 @@
-# ProjectPathValidator
-#
-# Custom validator for GitLab project path values.
-#
-# Values are checked for formatting and exclusion from a list of reserved path
-# names.
-#
-# This is basically the same as the `NamespaceValidator` but it skips the validation
-# of the format with `Gitlab::Regex.namespace_regex`. The format of projects
-# is validated in the class itself.
-class ProjectPathValidator < NamespaceValidator
-  def self.valid?(value)
-    !reserved?(value)
-  end
-
-  def self.reserved?(value, type: :wildcard)
-    super(value, type: :wildcard)
-  end
-
-  delegate :reserved?, to: :class
-
-  def validate_each(record, attribute, value)
-    if reserved?(value)
-      record.errors.add(attribute, "#{value} is a reserved name")
-    end
-  end
-end

lib/constraints/project_url_constrainer.rb

@@ -4,7 +4,7 @@ class ProjectUrlConstrainer
     project_path = request.params[:project_id] || request.params[:id]
     full_path = namespace_path + '/' + project_path
 
-    unless ProjectPathValidator.valid?(project_path)
+    unless NamespaceValidator.valid_full_path?(full_path)
       return false
     end