Properly fire update_email hook after commit which changes user email

app/models/concerns/track_saved_changes.rb

@@ -0,0 +1,50 @@
+# https://github.com/ccmcbeck/after-commit
+module TrackSavedChanges
+  extend ActiveSupport::Concern
+
+  included do
+    # expose the details if consumer wants to do more
+    attr_reader :saved_changes_history, :saved_changes_unfiltered
+    after_initialize :reset_saved_changes
+    after_save :track_saved_changes
+  end
+
+  # on initalize, but useful for fine grain control
+  def reset_saved_changes
+    @saved_changes_unfiltered = {}
+    @saved_changes_history = []
+  end
+
+  # filter out any changes that result in the original value
+  def saved_changes
+    @saved_changes_unfiltered.reject { |k,v| v[0] == v[1] }
+  end
+
+  private
+
+  # on save
+  def track_saved_changes
+    # maintain an array of ActiveModel::Dirty.changes
+    @saved_changes_history << changes.dup
+    # accumulate the most recent changes
+    @saved_changes_history.last.each_pair { |k, v| track_saved_change k, v }
+  end
+
+  # v is an an array of [prev, current]
+  def track_saved_change(k, v)
+    if @saved_changes_unfiltered.key? k
+      @saved_changes_unfiltered[k][1] = track_saved_value v[1]
+    else
+      @saved_changes_unfiltered[k] = v.dup
+    end
+  end
+
+  # type safe dup inspred by http://stackoverflow.com/a/20955038
+  def track_saved_value(v)
+    begin
+      v.dup
+    rescue TypeError
+      v
+    end
+  end
+end