Don't use post_init signal for initialize tracker

AUTHORS.rst

@@ -104,3 +104,4 @@
 | Éric Araujo <merwok@netwok.org>
 | Őry Máté <ory.mate@cloud.bme.hu>
 | Nafees Anwar <h.nafees.anwar@gmail.com>
+| meanmail <github@meanmail.dev>

docs/utilities.rst

@@ -328,9 +328,9 @@ FieldTracker implementation details
 
 This is how ``FieldTracker`` tracks field changes on ``instance.save`` call.
 
-1. In ``class_prepared`` handler ``FieldTracker`` patches ``save_base`` and
+1. In ``class_prepared`` handler ``FieldTracker`` patches ``save_base``,
-   ``refresh_from_db`` methods to reset initial state for tracked fields.
+   ``refresh_from_db`` and ``__init__`` methods to reset initial state for tracked fields.
-2. In ``post_init`` handler ``FieldTracker`` saves initial values for tracked
+2. In the patched ``__init__`` method ``FieldTracker`` saves initial values for tracked
    fields.
 3. ``MyModel.save`` changes ``update_fields`` in order to store auto updated
    ``modified`` timestamp. Complete list of saved fields is now known.

model_utils/tracker.py

@@ -343,7 +343,7 @@ class FieldTracker:
             wrapped_descriptor = wrapper_cls(field_name, descriptor, self.attname)
             setattr(sender, field_name, wrapped_descriptor)
         self.field_map = self.get_field_map(sender)
-        models.signals.post_init.connect(self.initialize_tracker)
+        self.patch_init(sender)
         self.model_class = sender
         setattr(sender, self.name, self)
         self.patch_save(sender)
@@ -356,6 +356,16 @@ class FieldTracker:
         tracker.set_saved_fields()
         instance._instance_initialized = True
 
+    def patch_init(self, model):
+        original = getattr(model, '__init__')
+
+        @wraps(original)
+        def inner(instance, *args, **kwargs):
+            original(instance, *args, **kwargs)
+            self.initialize_tracker(model, instance)
+
+        setattr(model, '__init__', inner)
+
     def patch_save(self, model):
         self._patch(model, 'save_base', 'update_fields')
         self._patch(model, 'refresh_from_db', 'fields')