Stamp the git tag or short commit in a plain docker build (closes #46)

A plain `docker build .` stamped `unknown` into the page footer:
.dockerignore left out .git, and the Dockerfile built without the -X
flags. The context now carries .git without .git/config, which can hold
a credential. The build stage takes the VERSION build argument when one
is given, otherwise `git describe --tags --always`, fails the build if
.git is present and no version comes out, and stamps it together with
the full commit the footer links to. `make build` now uses
`git describe` as well, and script/docker is the current shared copy.

Model: opus-5-5

.dockerignore

@@ -1,7 +1,11 @@
 # Docker does not read .gitignore, and a pattern here matches from the root of
 # the build context only: a pattern meant for every directory needs `**/`.
 
-.git
+# .git is sent without its config. Without a VERSION build argument the
+# stage that compiles runs `git describe --tags --always` on .git, which
+# does not need .git/config; that file can hold a credential, such as a
+# password in a remote URL or the token the CI checkout step stores there.
+.git/config
 
 # Local build and debug output: `make build`, `make run`, `make asupdate`, test
 # binaries, coverage profiles and source archives.

Dockerfile

@@ -40,8 +40,23 @@ RUN go mod download && go mod vendor
 # installed above. The suite is offline (the live-feed test is opt-in).
 RUN make test
 
-# Build the binary with CGO enabled (required for sqlite3)
-RUN CGO_ENABLED=1 GOOS=linux go build -o /routewatch ./cmd/routewatch
+# Build the binary with CGO enabled (required for sqlite3). The version the
+# page footer shows is the VERSION build argument when one is given, otherwise
+# `git describe --tags --always` of the .git in the build context (git comes
+# with this image): the tag on a tagged commit, tag-N-gHASH after one, the
+# short commit when no tag is reachable. A context that carries .git and still
+# yields no version fails the build. The footer links to the full commit.
+ARG VERSION
+RUN version="${VERSION:-$(git describe --tags --always || echo unknown)}"; \
+    if [ -e .git ] && { [ -z "$version" ] || [ "$version" = dev ] || \
+        [ "$version" = unknown ]; }; then \
+        echo "no version could be derived although the build context carries .git" >&2; \
+        exit 1; \
+    fi; \
+    CGO_ENABLED=1 GOOS=linux go build -o /routewatch -ldflags "\
+        -X git.eeqj.de/sneak/routewatch/internal/version.GitRevision=$(git rev-parse --verify HEAD || echo unknown) \
+        -X git.eeqj.de/sneak/routewatch/internal/version.GitRevisionShort=$version" \
+        ./cmd/routewatch
 
 # Create source archive with vendored dependencies
 RUN tar --zstd -cf /routewatch-source.tar.zst \

Makefile

@@ -2,7 +2,7 @@ export DEBUG = routewatch
 
 # Git revision for version embedding
 GIT_REVISION := $(shell git rev-parse HEAD 2>/dev/null || echo "unknown")
-GIT_REVISION_SHORT := $(shell git rev-parse --short HEAD 2>/dev/null || echo "unknown")
+GIT_REVISION_SHORT := $(shell git describe --tags --always 2>/dev/null || echo "unknown")
 VERSION_PKG := git.eeqj.de/sneak/routewatch/internal/version
 LDFLAGS := -X $(VERSION_PKG).GitRevision=$(GIT_REVISION) -X $(VERSION_PKG).GitRevisionShort=$(GIT_REVISION_SHORT)
 

TODO.md

@@ -28,6 +28,11 @@ The other open issue is https://git.eeqj.de/sneak/routewatch/issues/30.
 
 # Completed Steps
 
+- 2026-10-02: a plain `docker build .` stamps the commit's tag or short
+  commit (`git describe --tags --always`) into the page footer instead of
+  `unknown`: `.dockerignore` sends `.git` without `.git/config`, a `VERSION`
+  build argument takes precedence, and `make build` stamps the same value
+  (closes #46)
 - 2026-09-29: the entrypoint creates the data directory if it is missing and
   stops the start if a step fails; README "Running under upaas" no longer
   asks for the host directory to be created first (closes #42)

internal/version/version.go

@@ -7,7 +7,8 @@ package version
 var (
 	// GitRevision is the git commit hash
 	GitRevision = "unknown"
-	// GitRevisionShort is the short git commit hash (7 chars)
+	// GitRevisionShort is the version the page footer shows: the tag or
+	// short commit hash from `git describe --tags --always`
 	GitRevisionShort = "unknown"
 )
 

script/docker

@@ -1,7 +1,8 @@
 #!/bin/sh
 # script/docker: build the Docker image tagged with the project name.
 # Identical in all repos; the tag comes from script/projectname.
-# Generic: needs no adaptation.
+# --no-cache because the gate phases the final stage depends on are RUN
+# steps, and a cached one is a check that did not run.
 set -eu
 
 SCRIPT_DIR="$(cd "$(dirname "$0")" && pwd -P)"
@@ -9,7 +10,15 @@ ROOT="$(cd "$SCRIPT_DIR/.." && pwd -P)"
 
 main() {
     cd "$ROOT"
-    docker build -t "$("$SCRIPT_DIR/projectname")" .
+    # Own line: a failing command substitution inside an argument does
+    # not trip `set -e`, so the inline form degrades silently to an
+    # empty constant. The VERSION build argument takes precedence over
+    # the version a build stage derives from the .git in the context.
+    version="$(git describe --tags --always --dirty 2>/dev/null || true)"
+    [ -n "$version" ] || version="unknown"
+    docker build --no-cache \
+        --build-arg VERSION="$version" \
+        -t "$("$SCRIPT_DIR/projectname")" .
 }
 
 main "$@"