Remove BUILDARCH and stamp the git version in Docker builds (closes #107, closes #109)

The Makefile no longer passes a build architecture; it set a variable that
does not exist, and the architecture is available at run time.

A plain docker build now stamps neoircd with the tag or short commit:
.dockerignore sends .git, without its config, and the builder takes the
version from the VERSION build arg when given, otherwise from git describe.
With .git present, an empty, dev or unknown version fails the build.

Model: opus-5-5

.dockerignore

@@ -1,4 +1,5 @@
-.git
+# .git is sent so the build can stamp the version, without its config.
+.git/config
 *.md
 !README.md
 neoircd

Dockerfile

@@ -39,8 +39,19 @@ COPY --from=web-builder /web/dist/ web/dist/
 RUN make test
 
 # Build static binaries (no cgo needed at runtime — modernc.org/sqlite is pure Go)
-ARG VERSION=dev
-RUN CGO_ENABLED=0 go build -trimpath -ldflags="-s -w -X main.Version=${VERSION}" -o /neoircd ./cmd/neoircd/
+#
+# neoircd is stamped with the VERSION build arg when one is given, otherwise
+# with the tag or short commit from the .git in the build context. With .git
+# present, a version that is still empty, dev or unknown fails the build.
+ARG VERSION
+RUN VERSION="${VERSION:-$(git describe --tags --always)}"; \
+    if [ -e .git ]; then \
+        case "$VERSION" in ""|dev|unknown) \
+            echo "version is '$VERSION' although .git is present" >&2; \
+            exit 1 ;; \
+        esac; \
+    fi; \
+    CGO_ENABLED=0 go build -trimpath -ldflags="-s -w -X main.Version=${VERSION}" -o /neoircd ./cmd/neoircd/
 RUN CGO_ENABLED=0 go build -trimpath -ldflags="-s -w" -o /neoirc-cli ./cmd/neoirc-cli/
 
 # Runtime stage

Makefile

@@ -2,8 +2,7 @@
 
 BINARY := neoircd
 VERSION := $(shell git describe --tags --always --dirty 2>/dev/null || echo "dev")
-BUILDARCH := $(shell go env GOARCH)
-LDFLAGS := -X main.Version=$(VERSION) -X main.Buildarch=$(BUILDARCH)
+LDFLAGS := -X main.Version=$(VERSION)
 
 all: check build