Report the version: docker build . stamps the git tag or short commit (closes #7)

attrsum --version now prints the git tag or short commit. make build
stamps it with -X from git describe, and the Dockerfile takes the VERSION
build argument when given, otherwise git describe --tags --always on the
.git in the build context, failing if .git is present and no version
comes out. A new .dockerignore, the canonical one, keeps .git/config out
of the context. script/docker is replaced with the canonical copy.

Model: opus-5-5

.dockerignore

@@ -0,0 +1,60 @@
+# .dockerignore does NOT use .gitignore semantics. Docker matches with
+# moby/patternmatcher: filepath.Match plus `**`, so `*` does not cross
+# `/` and an unprefixed pattern is anchored at the context root. Every
+# depth-independent pattern therefore needs `**/`, or `config/.env` and
+# `certs/server.key` still ship while this file reads as solved. Only
+# genuinely root-anchored entries go unprefixed. Never transplant these
+# into .gitignore, where `**/` is wrong.
+#
+# Matching is case-sensitive, so secrets use character ranges rather
+# than an ALL-CAPS twin, which would still miss `Server.Key`.
+#
+# Extend with this repo's own host-built artifacts, written anchored:
+# `/myapp`, never `**/myapp`, which also matches `cmd/myapp/` and
+# deletes the package directory from the context.
+
+# .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
+
+# Agent scratch: one full checkout of the repo per in-flight agent.
+# Anchored because it occurs once where agents run at the repo root.
+# KNOWN GAP: a repo running agents in subdirectories still ships
+# `services/api/.claude/` and must add its own anchored entry.
+.claude
+
+# Environment files. `*.env` covers bare `.env` and the `prod.env`
+# convention. Re-include a committed template with a negation if the
+# build needs one: `!docs/example.env`.
+**/*.[eE][nN][vV]
+**/.[eE][nN][vV].*
+**/.[eE][nN][vV][rR][cC]
+
+# Private keys and the bundles carrying them. Public certificates
+# (*.crt, *.cer) are deliberately absent: they are legitimate inputs.
+**/*.[pP][eE][mM]
+**/*.[kK][eE][yY]
+**/*.[pP]12
+**/*.[pP][fF][xX]
+**/[iI][dD]_[rR][sS][aA]
+**/[iI][dD]_[dD][sS][aA]
+**/[iI][dD]_[eE][cC][dD][sS][aA]
+**/[iI][dD]_[eE][dD]25519
+
+# Dependencies: restored inside the image, never copied in.
+**/node_modules
+
+# OS metadata.
+**/.DS_Store
+**/Thumbs.db
+
+# Editor state: never a build input, and it churns COPY.
+**/*.swp
+**/*.swo
+**/*~
+**/*.bak
+**/.idea
+**/.vscode
+**/*.sublime-*

Dockerfile

@@ -29,7 +29,21 @@ RUN make check
 
 # Build the binary (still as the unprivileged user: it owns /src, so git VCS
 # stamping sees consistent ownership).
-RUN make build
+#
+# The version stamped into the binary: the VERSION build argument when one
+# is given, otherwise `git describe --tags --always` of the .git the build
+# context carries: the tag on a tagged commit, tag-N-gHASH on a commit after
+# one, the short commit when no tag is reachable. A context that carries .git
+# and still yields no version fails the build. With neither, as from a source
+# tarball, the binary reports dev.
+ARG VERSION
+RUN version="${VERSION:-$(git describe --tags --always)}"; \
+    if [ -e .git ] && { [ -z "$version" ] || [ "$version" = dev ] || \
+        [ "$version" = unknown ]; }; then \
+        echo "no version could be derived although the build context carries .git" >&2; \
+        exit 1; \
+    fi; \
+    make build VERSION="${version:-dev}"
 
 # Runtime stage
 # alpine 3.21, 2026-02-28

Makefile

@@ -2,6 +2,11 @@
 
 TESTDIR := $(HOME)/Documents/_SYSADMIN/cyberdyne
 
+# The version `make build` stamps into the binary: the git tag or short
+# commit, -dirty with uncommitted changes. `make build VERSION=x` stamps x,
+# which is how the Dockerfile passes its version in.
+VERSION ?= $(shell git describe --tags --always --dirty 2>/dev/null || echo dev)
+
 # Standard targets are thin shims; the implementations live in script/
 # per the scripts-to-rule-them-all pattern.
 
@@ -35,7 +40,7 @@ hooks:
 	@script/install-precommit
 
 build: clean
-	@go build .
+	@go build -ldflags "-X main.Version=$(VERSION)" .
 
 clean:
 	@rm -f attrsum

TODO.md

@@ -26,6 +26,9 @@ $(HOME)/Documents/_SYSADMIN/cyberdyne path.
 
 # Completed Steps
 
+* 2026-10-02: `attrsum --version` reports the git tag or short commit,
+    stamped by `make build` and by a plain `docker build .` of a clone;
+    `.dockerignore` sends `.git` without `.git/config`
 * 2026-02-02: correctness pass: track actual bytes read instead of
     stale file size, atomic failure tracking in ProcessCheck, detect
     file modification during checksum (TOCTOU), propagate countFiles

attrsum.go

@@ -36,6 +36,10 @@ const (
 	progressThrottle = 250 * time.Millisecond
 )
 
+// Version is the git tag or short commit, set at link time with -X by
+// `make build`. A build that does not set it reports dev.
+var Version = "dev" //nolint:gochecknoglobals // set at link time with -X
+
 // Sentinel errors returned by the command implementations.
 var (
 	errNoPaths           = errors.New("no paths provided")
@@ -103,6 +107,7 @@ func main() {
 	rootCmd := &cobra.Command{
 		Use:     "attrsum",
 		Short:   "Compute and verify file checksums via xattrs",
+		Version: Version,
 	}
 	rootCmd.SilenceUsage = true
 	rootCmd.SilenceErrors = true

script/docker

@@ -1,6 +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.
+# --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 "$0")" && pwd -P)"
@@ -8,7 +10,15 @@ ROOT="$(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 "$@"