Commit field back population migration

corehq/apps/hqadmin/migrations/0018_back_populate_deploy_commit.py

@@ -0,0 +1,35 @@
+# Generated by Django 2.2.13 on 2020-07-30 18:59
+
+from django.db import migrations
+from corehq.util.django_migrations import skip_on_fresh_install
+
+
+@skip_on_fresh_install
+def back_populate(apps, schema_editor):
+    HqDeploy = apps.get_model('hqadmin', 'hqdeploy')
+    for deploy in HqDeploy.objects.all():
+        if deploy.diff_url and not deploy.commit:
+            deploy.commit = _get_commit_from_url(deploy.diff_url)
+            deploy.save()
+
+
+def _get_commit_from_url(diff_url):
+    try:
+        ref_comparison = diff_url.split('/')[-1]
+        last_deploy_sha, current_deploy_sha = ref_comparison.split('...')
+        return current_deploy_sha
+    except ValueError:
+        # print('not a real diff_url', diff_url)
+        return None
+
+
+class Migration(migrations.Migration):
+
+    dependencies = [
+        ('hqadmin', '0017_hqdeploy_commit'),
+    ]
+
+    operations = [
+        migrations.RunPython(
+            back_populate, reverse_code=migrations.RunPython.noop, elidable=True),
+    ]