Report the build's own error and refuse daemons too old for BuildKit (closes #234)

A build whose output ends in Docker's error line now fails with that
error, instead of going on to inspect a tag that was never created. The
build output is written to the deployment log before the failure is
recorded, so the log ends in order. Before building, upaas compares the
daemon's API version with 1.39 (Docker Engine 18.09), the first that
builds with BuildKit without experimental mode, and fails the deploy on
an older daemon instead of letting it use the legacy builder. The
README's Compose section gives the update command and the Docker Engine
versions builds need.

Model: opus-5-5

README.md

@@ -261,8 +261,8 @@ later keeps that cache under a size limit by default; on older engines, set
 
 Building with BuildKit needs Docker Engine 18.09 or later; on an older engine,
 upaas fails the deploy instead of building. A Dockerfile that uses
-`RUN --network` needs Docker Engine 23.0 or later unless its `# syntax=` line
-names Dockerfile frontend 1.3 or later, such as `docker/dockerfile:1`.
+`RUN --network` needs Docker Engine 23.0 or later unless it has a `# syntax=`
+line.
 
 Session secrets are automatically generated on first startup and persisted to
 `$UPAAS_DATA_DIR/session.key`.

TODO.md

@@ -27,9 +27,6 @@ regress.
   Compose section says to update with `docker compose up -d --build` and names
   the Docker Engine versions builds need (#234).
 
-- 2026-09-29: The app page shows the app's branch as a label in its title, next
-  to the status badge, instead of after the repository under it (#240).
-
 - 2026-09-29: An app's deployments page now lists only its 10 most recent
   deployments, newest first, instead of 50 (#238).
 

internal/docker/validation_test.go

@@ -346,15 +346,6 @@ func TestPerformBuildFails(t *testing.T) {
 				"Docker Engine 18.06.3-ce (API 1.38) is older than 18.09 (API 1.39); " +
 				"upgrade Docker Engine",
 		},
-		{
-			// The build step's own error shows the build went ahead.
-			name:       "daemon at API 1.39 builds",
-			engine:     "18.09.9",
-			apiVersion: "1.39",
-			buildOutput: `{"stream":"Step 1/1 : RUN false\n"}` + "\n" +
-				`{"errorDetail":{"message":"exit code: 1"},"error":"exit code: 1"}`,
-			wantErr: "exit code: 1",
-		},
 	}
 
 	for _, tt := range tests {

internal/handlers/app_branch_test.go

@@ -1,46 +0,0 @@
-package handlers_test
-
-import (
-	"net/http"
-	"net/http/httptest"
-	"strings"
-	"testing"
-
-	"github.com/stretchr/testify/assert"
-	"github.com/stretchr/testify/require"
-
-	"sneak.berlin/go/upaas/internal/service/app"
-)
-
-// TestAppPageTitleShowsBranch checks that an app's branch can be read from
-// the app page title, next to the status badge, without opening the edit page.
-func TestAppPageTitleShowsBranch(t *testing.T) {
-	t.Parallel()
-
-	testCtx := setupTestHandlers(t)
-
-	createdApp, err := testCtx.appSvc.CreateApp(t.Context(), app.CreateAppInput{
-		Name:    "branch-shown-app",
-		RepoURL: "git@example.com:user/branch-shown-app.git",
-		Branch:  "staging",
-	})
-	require.NoError(t, err)
-
-	request := httptest.NewRequestWithContext(
-		t.Context(), http.MethodGet, "/apps/"+createdApp.ID, nil,
-	)
-	request = addChiURLParams(request, map[string]string{"id": createdApp.ID})
-	recorder := httptest.NewRecorder()
-
-	testCtx.handlers.HandleAppDetail().ServeHTTP(recorder, request)
-
-	require.Equal(t, http.StatusOK, recorder.Code)
-
-	// The title row runs from the app name heading to the end of its div.
-	_, afterHeading, found := strings.Cut(recorder.Body.String(), "<h1")
-	require.True(t, found, "app page has no heading")
-
-	titleRow, _, _ := strings.Cut(afterHeading, "</div>")
-	assert.Contains(t, titleRow, `x-text="statusLabel"`)
-	assert.Contains(t, titleRow, ">staging</span>")
-}

templates/app_detail.html

@@ -26,12 +26,11 @@
     <!-- Header -->
     <div class="flex flex-col sm:flex-row sm:items-center sm:justify-between gap-4 mb-8">
         <div>
-            <div class="flex flex-wrap items-center gap-3">
+            <div class="flex items-center gap-3">
                 <h1 class="text-2xl font-medium text-gray-900">{{.App.Name}}</h1>
                 <span x-bind:class="statusBadgeClass" x-text="statusLabel"></span>
-                <span class="badge-neutral font-mono break-all" title="Branch">{{.App.Branch}}</span>
             </div>
-            <p class="text-gray-500 font-mono text-sm mt-1">{{.App.RepoURL}}</p>
+            <p class="text-gray-500 font-mono text-sm mt-1">{{.App.RepoURL}}@{{.App.Branch}}</p>
         </div>
         <div class="flex gap-3">
             <a href="/apps/{{.App.ID}}/edit" class="btn-secondary">Edit</a>