Add snapshot form

nummi/main/models.py

@@ -94,6 +94,7 @@ class Snapshot(models.Model):
         if not only_super:
             _prev = (
                 self.__class__.objects.order_by("-date")
+                .exclude(id=self.id)
                 .filter(date__lt=self.date)
                 .first()
             )
@@ -139,3 +140,9 @@ class Snapshot(models.Model):
 
     class Meta:
         ordering = ["-date"]
+
+
+class SnapshotForm(ModelForm):
+    class Meta:
+        model = Snapshot
+        fields = ["date", "value"]