Tag built images with the commit's short hash (closes #239)

Builds are tagged upaas-<app>:<short hash>, git's short form of
the commit checked out, instead of the deployment number. The clone
prints the short hash and fails without one.

A redeploy of a commit gives the tag to the new image. The cleanup
after a deploy now also finds the app's untagged images among those
its deployments recorded, and removes them by ID once the app neither
runs them nor would roll back to them. It keeps every image any app
uses, since apps that build the same commit can share one.

commit_sha is now saved on update so manual deploys keep the commit
read from the clone.

Model: opus-5-5

internal/models/models_test.go

@@ -564,6 +564,33 @@ func TestDeploymentMarkFinished(t *testing.T) {
 	assert.True(t, found.FinishedAt.Valid)
 }
 
+// TestDeploymentSaveStoresCommitSetAfterInsert checks that a commit set on a
+// deployment after it was first saved, as a manual deploy does once the clone
+// reads it, is stored by the next save.
+func TestDeploymentSaveStoresCommitSetAfterInsert(t *testing.T) {
+	t.Parallel()
+
+	testDB, cleanup := setupTestDB(t)
+	defer cleanup()
+
+	app := createTestApp(t, testDB)
+
+	deployment := models.NewDeployment(testDB)
+	deployment.AppID = app.ID
+
+	err := deployment.Save(context.Background())
+	require.NoError(t, err)
+
+	deployment.CommitSHA = sql.NullString{String: "abc123def456", Valid: true}
+
+	err = deployment.Save(context.Background())
+	require.NoError(t, err)
+
+	found, err := models.FindDeployment(context.Background(), testDB, deployment.ID)
+	require.NoError(t, err)
+	assert.Equal(t, "abc123def456", found.CommitSHA.String)
+}
+
 func TestDeploymentFindByAppID(t *testing.T) {
 	t.Parallel()