Add "revision" number to report model

- Auto-increments whenever the model is saved

InvenTree/company/tests.py

@@ -1,3 +1,6 @@
+# -*- coding: utf-8 -*-
+from __future__ import unicode_literals
+
 from django.test import TestCase
 from django.core.exceptions import ValidationError
 

InvenTree/report/admin.py

@@ -8,7 +8,7 @@ from .models import ReportSnippet, TestReport, ReportAsset
 
 class ReportTemplateAdmin(admin.ModelAdmin):
 
-    list_display = ('name', 'description', 'template', 'filters', 'enabled')
+    list_display = ('name', 'description', 'template', 'filters', 'enabled', 'revision')
 
 
 class ReportSnippetAdmin(admin.ModelAdmin):

InvenTree/report/migrations/0009_testreport_revision.py

@@ -0,0 +1,18 @@
+# Generated by Django 3.0.7 on 2021-02-05 00:53
+
+from django.db import migrations, models
+
+
+class Migration(migrations.Migration):
+
+    dependencies = [
+        ('report', '0008_auto_20210204_2100'),
+    ]
+
+    operations = [
+        migrations.AddField(
+            model_name='testreport',
+            name='revision',
+            field=models.PositiveIntegerField(default=1, help_text='Report revision number (auto-increments)', verbose_name='Revision'),
+        ),
+    ]

InvenTree/report/migrations/0010_auto_20210205_1201.py

@@ -0,0 +1,18 @@
+# Generated by Django 3.0.7 on 2021-02-05 01:01
+
+from django.db import migrations, models
+
+
+class Migration(migrations.Migration):
+
+    dependencies = [
+        ('report', '0009_testreport_revision'),
+    ]
+
+    operations = [
+        migrations.AlterField(
+            model_name='testreport',
+            name='revision',
+            field=models.PositiveIntegerField(default=1, editable=False, help_text='Report revision number (auto-increments)', verbose_name='Revision'),
+        ),
+    ]

InvenTree/report/models.py

@@ -62,6 +62,13 @@ class ReportBase(models.Model):
     class Meta:
         abstract = True
 
+    def save(self, *args, **kwargs):
+
+        # Increment revision number
+        self.revision += 1
+
+        super().save()
+
     def __str__(self):
         return "{n} - {d}".format(n=self.name, d=self.description)
 
@@ -113,6 +120,13 @@ class ReportBase(models.Model):
         help_text=_("Report template description")
     )
 
+    revision = models.PositiveIntegerField(
+        default=1,
+        verbose_name=_("Revision"),
+        help_text=_("Report revision number (auto-increments)"),
+        editable=False,
+    )
+
 
 class ReportTemplateBase(ReportBase):
     """