revision: track pull request head SHA (bug 2005795)

- add Revision.pull_head_sha field
- add migrations
- store pull_head_sha when landing job is created

Author: zzzeid

src/lando/api/views.py

@@ -282,6 +282,7 @@ class Form(forms.Form):
         }
         revision = Revision.objects.create(
             pull_number=pull_request.number,
+            pull_head_sha=pull_request.head_sha,
             patches=pull_request.patch,
             patch_data=patch_data,
         )

src/lando/main/migrations/0040_revision_pull_head_sha.py

@@ -0,0 +1,18 @@
+# Generated by Django 5.2.8 on 2025-12-12 18:42
+
+from django.db import migrations, models
+
+
+class Migration(migrations.Migration):
+
+    dependencies = [
+        ("main", "0039_alter_repo_hooks_PreventDotGithubCheck"),
+    ]
+
+    operations = [
+        migrations.AddField(
+            model_name="revision",
+            name="pull_head_sha",
+            field=models.CharField(blank=True, max_length=40, null=True),
+        ),
+    ]

src/lando/main/models/revision.py

@@ -50,6 +50,9 @@ class Revision(BaseModel):
     # GitHub pull request number, if this is a pull request.
     pull_number = models.IntegerField(blank=True, null=True)
 
+    # GitHub pull request head SHA, if this is a pull request.
+    pull_head_sha = models.CharField(max_length=40, blank=True, null=True)
+
     # The generated patch with Mercurial metadata format.
     # This patch is generated by combining a diff and patch metadata.
     patch = models.TextField(blank=True, default="")