Explain namespace clearn regex.

app/models/namespace.rb

@@ -60,10 +60,15 @@ class Namespace < ActiveRecord::Base
 
     def clean_path(path)
       path = path.dup
+      # Get the email username by removing everything after an `@` sign.
       path.gsub!(/@.*\z/,             "")
+      # Usernames can't end in .git, so remove it.
       path.gsub!(/\.git\z/,           "")
+      # Remove dashes at the start of the username.
       path.gsub!(/\A-+/,              "")
+      # Remove periods at the end of the username.
       path.gsub!(/\.+\z/,             "")
+      # Remove everything that's not in the list of allowed characters.
       path.gsub!(/[^a-zA-Z0-9_\-\.]/, "")
 
       # Users with the great usernames of "." or ".." would end up with a blank username.

db/migrate/20150421120000_remove_periods_at_ends_of_usernames.rb

@@ -9,10 +9,15 @@ class RemovePeriodsAtEndsOfUsernames < ActiveRecord::Migration
 
       def clean_path(path)
         path = path.dup
+        # Get the email username by removing everything after an `@` sign.
         path.gsub!(/@.*\z/,             "")
+        # Usernames can't end in .git, so remove it.
         path.gsub!(/\.git\z/,           "")
+        # Remove dashes at the start of the username.
         path.gsub!(/\A-+/,              "")
+        # Remove periods at the end of the username.
         path.gsub!(/\.+\z/,             "")
+        # Remove everything that's not in the list of allowed characters.
         path.gsub!(/[^a-zA-Z0-9_\-\.]/, "")
 
         # Users with the great usernames of "." or ".." would end up with a blank username.