Let a plain docker build pass and stamp the git version (closes #57)

The size tests skip a case whose secret needs more locked memory than
RLIMIT_MEMLOCK allows: memguard panics otherwise, and a plain
`docker build .` runs under an 8 MiB limit. script/cibuild still runs
every case.

The build stage stamps the VERSION build argument, else
`git describe --tags --always`, and fails when .git is present but
yields no version. `make build` stamps `git describe` too instead of
the fixed 0.1.0. .dockerignore keeps .git/config out; script/docker is
now the canonical copy.

Model: opus-5-5

.dockerignore

@@ -1,3 +1,9 @@
+# .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
+
 # Build artifacts
 secret
 coverage.out

Dockerfile

@@ -27,7 +27,20 @@ RUN go mod download
 COPY . .
 
 RUN make test
-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.
+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 3.23 (2026-03-10)

Makefile

@@ -2,7 +2,7 @@ export CGO_ENABLED=1
 export DOCKER_HOST := ssh://root@ber1app1.local
 
 # Version information
-VERSION := 0.1.0
+VERSION := $(shell git describe --tags --always --dirty 2>/dev/null || echo "dev")
 GIT_COMMIT := $(shell git rev-parse HEAD 2>/dev/null || echo "unknown")
 LDFLAGS := -X 'git.eeqj.de/sneak/secret/internal/cli.Version=$(VERSION)' \
            -X 'git.eeqj.de/sneak/secret/internal/cli.GitCommit=$(GIT_COMMIT)'

TODO.md

@@ -25,6 +25,14 @@ Bring the repo into policy compliance in one commit:
 
 # Completed Steps
 
+- 2026-10-02: A plain `docker build .` builds again: the size tests
+  skip a case that needs more locked memory than the limit allows,
+  and run every case under `script/cibuild`. The image stamps the
+  `VERSION` build argument, else `git describe --tags --always`, into
+  `Version`, and fails if `.git` is present but yields no version;
+  `make build` stamps `git describe` too, not a fixed `0.1.0`.
+  `.dockerignore` keeps `.git/config` out; `script/docker` is the
+  canonical copy.
 - 2026-08-07: Updated golangci-lint to v2.12.2 with the canonical
   `.golangci.yml` (all linters enabled minus the standard disable
   list, `lll` 88, tests linted); bumped the `Dockerfile` lint-stage

go.mod

@@ -16,6 +16,7 @@ require (
 	github.com/stretchr/testify v1.8.4
 	github.com/tyler-smith/go-bip39 v1.1.0
 	golang.org/x/crypto v0.38.0
+	golang.org/x/sys v0.33.0
 	golang.org/x/term v0.32.0
 )
 
@@ -31,7 +32,6 @@ require (
 	github.com/mattn/go-isatty v0.0.20 // indirect
 	github.com/pmezard/go-difflib v1.0.0 // indirect
 	github.com/spf13/pflag v1.0.6 // indirect
-	golang.org/x/sys v0.33.0 // indirect
 	golang.org/x/text v0.25.0 // indirect
 	gopkg.in/yaml.v3 v3.0.1 // indirect
 )

internal/cli/secrets_size_test.go

@@ -17,11 +17,38 @@ import (
 	"github.com/spf13/cobra"
 	"github.com/stretchr/testify/assert"
 	"github.com/stretchr/testify/require"
+	"golang.org/x/sys/unix"
 )
 
 // testVaultName is the vault name used by the size tests.
 const testVaultName = "test-vault"
 
+// lockedBytesPerSecretByte bounds the locked memory that storing a secret
+// holds at once: the buffers it is read into reach up to 1.5 times its
+// size, and they are then copied into one more buffer of its size.
+const lockedBytesPerSecretByte = 3
+
+// skipIfLockedMemoryTooLow skips the test when the locked-memory limit
+// (RLIMIT_MEMLOCK) cannot hold a secret of size bytes. memguard panics,
+// ending the whole test run, when it cannot lock a buffer, and a plain
+// `docker build .` runs the tests under an 8 MiB limit.
+func skipIfLockedMemoryTooLow(t *testing.T, size int) {
+	t.Helper()
+
+	var limit unix.Rlimit
+
+	err := unix.Getrlimit(unix.RLIMIT_MEMLOCK, &limit)
+	require.NoError(t, err)
+
+	//nolint:gosec // test sizes are never negative
+	need := lockedBytesPerSecretByte * uint64(size)
+	if limit.Cur < need {
+		t.Skipf("a %d-byte secret needs up to %d bytes of locked memory, "+
+			"more than the locked-memory limit (RLIMIT_MEMLOCK) of %d bytes",
+			size, need, limit.Cur)
+	}
+}
+
 // newSizeTestVault creates an in-memory vault unlocked with the test
 // mnemonic and returns the filesystem and vault.
 //
@@ -59,6 +86,7 @@ func newSizeTestVault(t *testing.T) (afero.Fs, *vault.Vault) {
 // verifies the outcome.
 func runAddSecretSizeCase(t *testing.T, size int, wantErr bool, errMsg string) {
 	t.Helper()
+	skipIfLockedMemoryTooLow(t, size)
 
 	fs, vlt := newSizeTestVault(t)
 
@@ -110,6 +138,7 @@ func runAddSecretSizeCase(t *testing.T, size int, wantErr bool, errMsg string) {
 // verifies the outcome.
 func runImportSecretSizeCase(t *testing.T, size int, wantErr bool, errMsg string) {
 	t.Helper()
+	skipIfLockedMemoryTooLow(t, size)
 
 	fs, vlt := newSizeTestVault(t)
 
@@ -300,6 +329,8 @@ func TestAddSecretBufferGrowth(t *testing.T) {
 
 	for _, size := range sizes {
 		t.Run(fmt.Sprintf("size_%d", size), func(t *testing.T) {
+			skipIfLockedMemoryTooLow(t, size)
+
 			fs, vlt := newSizeTestVault(t)
 
 			// Create test data of exactly the specified size

script/cibuild

@@ -1,8 +1,9 @@
 #!/bin/sh
 # script/cibuild: run the CI build. The Dockerfile runs script/check
 # (via make check), so a successful build implies all checks pass.
-# The Gitea workflow runs this on push. The memlock ulimit is required
-# because the test suite uses memguard, which mlocks memory.
+# The Gitea workflow runs this on push. The memlock ulimit lets the tests
+# that lock large secrets in memory (memguard mlocks them) run; under the
+# lower limit of a plain `docker build .` they are skipped.
 set -eu
 
 ROOT="$(cd "$(dirname "$0")/.." && pwd -P)"

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 "$@"