PR #89 stopped script/cibuild replaying cached check layers, but left a
gap: a bare `docker build .` with no --build-arg still faked. An unset
ARG is an empty string, an empty string is a stable cache key, and the
check layers replay from it. That gap mattered because REPO_POLICIES.md
names `docker build .` verbatim as a command that must be green, so the
documented command was the one that lied.
Both check stages now carry `RUN [ -n "$CHECK_EPOCH" ] || exit 1`
immediately under their own ARG. Failed steps are never cached, so this
fails on every invocation rather than once - a bare build now stops with
a named error instead of reporting a green it did not earn. Each stage
needs its own guard because ARG scope is per-stage; a gate-carrying stage
without one is a silent hole if ordering ever changes.
The check RUNs now reference the value (`echo "check epoch: ${CHECK_EPOCH}"
&& make <target>`), so the cache miss is contractual rather than resting
on BuildKit's current treatment of unreferenced ARGs, and the epoch is
visible in the build log.
The epoch becomes "$(date +%s%N)$$" so concurrent invocations in the same
second cannot collide. busybox silently drops %N and exits 0, so $$ is
what makes it correct there. The bare-assignment form is retained
deliberately: inlining the substitution into --build-arg would, under
set -eu, yield an empty and therefore constant epoch without aborting.
script/docker gets the same treatment - it is not the gate, but two
entrypoints disagreeing about whether the tree is green is its own
hazard, and local builds are almost always warm.
Verified by negative control rather than inspection: a bare build fails
twice consecutively here and succeeds twice on the parent commit, so the
change is demonstrably not a no-op. The builder-stage guard was fired
directly with a targeted probe build, since the lint stage otherwise
fails first and would leave it unexercised.
script/cibuild was a bare `docker build .`. On an unchanged tree Docker
served the check RUN layers from cache, so make fmt-check, make lint and
make test never executed - and the build still exited 0. Measured at
221ms with zero ok lines and every check layer CACHED, against 162s for a
real run. CI showed the same signature: 6 second "successes" on main.
An ARG CHECK_EPOCH now sits immediately above the check RUNs in both
stages - each stage declares its own, since ARG scope is per-stage - and
script/cibuild passes a fresh value per invocation. Dependency and module
layers sit above the ARG and still cache, so this does not make every
build cold.
The epoch is assigned before the build rather than inlined into the
--build-arg. Under `set -eu` a command substitution that fails inside an
argument does not abort the script: CHECK_EPOCH would become an empty
string, an empty string is a constant, a constant CHECK_EPOCH restores
the cached false green, and the guard would silently disarm itself while
still exiting 0. As a bare assignment, set -e catches a failing date and
no build starts.
The README and Dockerfile state the guarantee conditionally. It holds per
build context and CHECK_EPOCH value, and depends on script/cibuild
passing a fresh one - a bare `docker build .` with no --build-arg still
replays the check layers from the second consecutive run onward. That
residual gap is tracked in #91 along with the remaining upstream
hardening.
Verification is recorded once, in the PR's verification comment, rather
than restated with differing numbers in three places.
script/lint ran bare golangci-lint from PATH while CI and the Dockerfile
pinned v2.12.2 by digest, so make lint and CI could disagree about
findings. That drift ran both directions: it produced two false green
claims during the lint remediation, and on an ambient 2.10.1 it also
reported four gosec findings on a tree CI linted clean.
script/lint now extracts the image reference - tag and digest - from the
Dockerfile lint stage FROM line and runs that exact image under docker.
The Dockerfile FROM line is the single source of truth for the linter
version; the duplicate pins in the Makefile deps target and in
script/bootstrap are removed rather than kept in sync.
A golangci-lint on PATH is used only when its version exactly equals the
pin, which is what makes the in-container lint stage work (the Dockerfile
runs make lint inside the pinned image, where there is no docker daemon).
Any other version, or none, goes through docker. When docker is
unavailable the script fails with an actionable message and never falls
back to a different linter version.
script/lint-fix delegates to script/lint --fix so autofixes come from the
pinned linter too. The container mounts persistent build and module
caches and runs as the invoking uid/gid.
Verified by reinstating the four historical nolint directives that 2.10.1
requires and 2.12.2 reports as unused: the old script passed on that tree
and the new one fails with four nolintlint findings.
