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

.dockerignore

@@ -1,11 +1,8 @@
-.git
+# .git is sent so that `make build` in the Dockerfile can stamp the commit into
+# upaas. List no tracked file here: git would see it as deleted in the build and
+# the version would end in -dirty.
 .env
 bin/
-.editorconfig
 .vscode/
 .idea/
 *.test
-LICENSE
-CONVENTIONS.md
-REPO_POLICIES.md
-README.md

Dockerfile

@@ -31,6 +31,7 @@ RUN go mod download
 COPY . .
 
 RUN make test
+# Takes the version from `git describe` on the .git copied in above.
 RUN make build
 
 # Runtime stage

README.md

@@ -226,6 +226,10 @@ This recipe serves plain HTTP, so `UPAAS_PLAINTEXT_HTTP=true` is required for
 setup and every other form to pass the CSRF origin check. Behind a
 TLS-terminating reverse proxy, drop that line.
 
+The image shows the commit it was built from (the `git describe` output) in the
+page footer, the startup log and `/health`. Build it from a git clone: without
+the `.git` directory it shows `dev`.
+
 ### Deploying with Docker Compose
 
 [`docker-compose.yml`](docker-compose.yml) builds the image from this repo and

TODO.md

@@ -27,6 +27,12 @@ regress.
   Compose section says to update with `docker compose up -d --build` and names
   the Docker Engine versions builds need (#234).
 
+- 2026-09-29: An image built from the `Dockerfile` now shows the commit it was
+  built from (the `git describe` output) in the footer and `/health` instead of
+  `dev`: `.dockerignore` no longer leaves out `.git`, nor any tracked file,
+  which git would count as deleted and mark `-dirty`. upaas now also logs its
+  version at startup; the logger's `Identify()` was never called (#236).
+
 - 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).
 

cmd/upaasd/main.go

@@ -52,6 +52,8 @@ func main() {
 			handlers.New,
 			server.New,
 		),
-		fx.Invoke(func(*server.Server) {}),
+		fx.Invoke(func(log *logger.Logger, _ *server.Server) {
+			log.Identify()
+		}),
 	).Run()
 }