Gate the build on Docker lint and test phases (closes #40, closes #30)

Per the owner ruling on issue 40, linting and testing are phases of the
main Dockerfile rather than a separate lint file. script/lint and
script/test build one phase each by name with caching disabled, and the
final stage copies a harmless file from each so the image cannot be built
unless both passed — template-app-go's ordering trick, extended to the
test phase. A stage that is not the last is built only when something
depends on it or --target names it, so the gates are invoked by name and
the edges kept. script/check runs the gates and builds no image;
script/cibuild bootstraps first, because CI runs it alone and fmt-check
is native. Every build in script/ is tagged and uncached. No config
verify step. Issue 30 closes too: a container has its own lint cache and
lock.

Model: opus-5

README.md

@@ -123,16 +123,17 @@ alpine. We provide:
 - `script/fmt` — format all markdown files with prettier (writes; native, not in
   a container)
 - `script/fmt-check` — check formatting (read-only; native)
-- `script/check` — run all checks: `test`, `lint`, `fmt-check`, then
-  `docker build -t prompts .` (our own extension; no `--no-cache` there, because
-  the two phases that build depends on were just built without it)
+- `script/check` — run all checks: `test`, `lint`, `fmt-check` (our own
+  extension); builds no image
 - `script/docker` —
   `docker build --no-cache --build-arg VERSION="$version" -t prompts .`, the tag
   coming from `script/projectname` (byte-identical across repos)
-- `script/cibuild` — cd to the repo root, compute `version` from `git describe`,
-  run `script/check`, then
-  `docker build --build-arg VERSION="$version" -t prompts .` (what CI runs; the
-  version is computed on the host because `.dockerignore` excludes `.git`)
+- `script/cibuild` — cd to the repo root, run `script/bootstrap`, run
+  `script/check`, compute `version` from `git describe`, then
+  `docker build --no-cache --build-arg VERSION="$version" -t prompts .` (what CI
+  runs; it bootstraps because CI checks out and runs this alone while
+  `script/fmt-check` is native, and the version is computed on the host because
+  `.dockerignore` excludes `.git`)
 - `script/precommit` — run by the git pre-commit hook (our own extension); calls
   `script/check`
 - `script/install-precommit` — installs the git pre-commit hook (our own

TODO.md

@@ -29,6 +29,8 @@ fmt-check, and commit.
   they pass. This also closes issue 30: a container has its own result cache and
   its own lock, so a lint verdict can no longer belong to another checkout. No
   separate lint Dockerfile, and no `golangci-lint config verify` step.
+  `script/check` runs the gates and nothing else, and `script/cibuild`
+  bootstraps first, since it is all CI runs and `script/fmt-check` is native.
 - 2026-09-08: Kept in-repo agent scratch out of the Docker build context and out
   of version control: `.claude/` is one full checkout of the repo per in-flight
   agent, and under `COPY . .` all of it was reaching the image. Also closed the

prompts/EXISTING_REPO_CHECKLIST.md

@@ -99,6 +99,10 @@ with your task.
       on the host.
 - [ ] Every `docker build` in `script/` is tagged — an untagged one leaves a
       dangling image behind on every run, on every host and CI runner
+- [ ] `script/cibuild` runs `script/bootstrap` before `script/check`, and builds
+      the image with `--no-cache`. Without the bootstrap the CI run dies in
+      `script/fmt-check`, which runs the formatter on the host and finds nothing
+      installed.
 - [ ] `script/bootstrap` installs no linter of its own — delete the block, its
       version variables and its call site. A JS repo's `yarn install` stays; it
       brings a linter along with every other dependency, and no verdict is taken
@@ -151,8 +155,9 @@ with your task.
 # Final
 
 - [ ] `make check` passes
-- [ ] `script/cibuild` succeeds and demonstrably executed the checks — a
-      sub-second build, or `CACHED` on a gate layer, means nothing ran
+- [ ] `script/cibuild` succeeds in a fresh clone with nothing installed, which
+      is what CI has, and demonstrably executed the checks — a sub-second build,
+      or `CACHED` on a gate layer, means nothing ran
 - [ ] A planted lint violation fails both `make lint` and a plain
       `docker build .`; revert it afterwards
 - [ ] Commit and merge fixes before starting your actual task

prompts/NEW_REPO_CHECKLIST.md

@@ -113,15 +113,18 @@ are thin shims calling them. Model scripts:
       container)
 - [ ] `script/fmt-check` / `make fmt-check` — checks formatting (read-only;
       native)
-- [ ] `script/check` / `make check` — runs `test`, `lint`, `fmt-check`, then
-      builds the image; must not modify files
+- [ ] `script/check` / `make check` — runs `test`, `lint`, `fmt-check`; must not
+      modify files
 - [ ] `script/projectname` — outputs the project name (used by `script/docker`
       for the image tag)
 - [ ] `script/docker` / `make docker` — builds Docker image, tagged via
       `script/projectname` (byte-identical across repos); `--no-cache`, plus the
       version as a build arg
-- [ ] `script/cibuild` — cd to repo root, run `script/check`, then
-      `docker build --build-arg VERSION="$version" .` (what CI runs)
+- [ ] `script/cibuild` — cd to repo root, run `script/bootstrap`, run
+      `script/check`, then
+      `docker build --no-cache --build-arg VERSION="$version" .` (what CI runs).
+      The bootstrap is required: CI checks out and runs this alone, and
+      `script/fmt-check` runs the formatter on the host.
 - [ ] Every `docker build` in `script/` is tagged, so no invocation leaves a
       dangling image behind
 - [ ] `script/precommit` — called by the pre-commit hook; runs `script/check`
@@ -135,8 +138,9 @@ are thin shims calling them. Model scripts:
 
 - [ ] `make check` passes
 - [ ] `make docker` succeeds
-- [ ] `script/cibuild` succeeds and demonstrably executed the checks — a
-      sub-second build, or `CACHED` on a gate layer, means nothing ran
+- [ ] `script/cibuild` succeeds in a fresh clone with nothing installed, which
+      is what CI has, and demonstrably executed the checks — a sub-second build,
+      or `CACHED` on a gate layer, means nothing ran
 - [ ] Plant a lint violation and confirm both `make lint` and a plain
       `docker build .` fail on it; revert. A plain build that passes proves the
       final stage is missing its `COPY --from=` edge to the gate phases.

prompts/REPO_POLICIES.md

@@ -60,12 +60,16 @@ style conventions are in separate documents:
   prerequisite since nvm requires bash. yarn is then pinned via
   `corepack prepare yarn@<version> --activate`. Never install "latest" or "lts";
   always exact versions. `script/cibuild` runs the CI build: it changes to the
-  repo root, runs `script/check`, and builds the image with the version; the
-  Gitea workflow calls it. Four further scripts are our own extensions to the
-  standard: `script/check` runs `script/test`, `script/lint` and
-  `script/fmt-check`, then builds the image; `script/precommit` is what the git
-  pre-commit hook runs, and it calls `script/check`; `script/install-precommit`
-  installs the git pre-commit hook (the `make hooks` target shims to it); and
+  repo root, runs `script/bootstrap`, runs `script/check`, and builds the image
+  with the version; the Gitea workflow calls it. **`script/cibuild` runs
+  `script/bootstrap` first**, because the workflow checks out the repo and runs
+  nothing else, while `script/fmt-check` runs the formatter on the host: on a
+  pristine checkout with nothing installed the run dies there, after the
+  containerised gates have passed. Four further scripts are our own extensions
+  to the standard: `script/check` runs `script/test`, `script/lint` and
+  `script/fmt-check`; `script/precommit` is what the git pre-commit hook runs,
+  and it calls `script/check`; `script/install-precommit` installs the git
+  pre-commit hook (the `make hooks` target shims to it); and
   `script/projectname` (literally that filename) simply outputs the project's
   name. Scripts that need the name call `script/projectname` — e.g.
   `script/docker` assembles its image tag from it — so those scripts stay
@@ -115,7 +119,7 @@ style conventions are in separate documents:
     plain `docker build .` builds the last stage alone and exits 0 having linted
     and tested nothing.
 
-    **Every `docker build` in `script/` is tagged**, here and in `script/check`,
+    **Every `docker build` in `script/` is tagged**, here and in
     `script/cibuild` and `script/docker`. An untagged build leaves a dangling
     image behind on every invocation, on every developer host and every CI
     runner; a tagged one replaces the previous image.
@@ -139,14 +143,13 @@ style conventions are in separate documents:
 - **Any build that runs checks is built with `--no-cache`.** Docker invalidates
   a `COPY` layer only when the copied content changes, so on an unchanged tree
   the check `RUN` is served from cache, nothing executes, and the build still
-  exits 0. `script/lint`, `script/test`, `script/cibuild` and `script/docker`
-  therefore pass `--no-cache`, and a bare `docker build .` is not evidence that
-  anything ran: a sub-second build reporting success is a cache hit, not a
-  result. The one build that may go through the cache is the image build inside
-  `script/check`, which runs immediately after the two gate phases were built
-  uncached and so reuses that run. Never invalidate by pruning —
-  `docker builder prune` and friends destroy a build cache shared with every
-  other build on the host.
+  exits 0. Every `docker build` in `script/` therefore passes `--no-cache`:
+  `script/lint`, `script/test`, `script/cibuild` and `script/docker` are the
+  four, and there is no fifth — `script/check` runs the two gate phases and
+  `script/fmt-check`, and builds no image of its own. A bare `docker build .` is
+  not evidence that anything ran: a sub-second build reporting success is a
+  cache hit, not a result. Never invalidate by pruning — `docker builder prune`
+  and friends destroy a build cache shared with every other build on the host.
 
 - **The gate phases are separate stages, and the build stage depends on both.**
   The lint phase is based on the `golangci/golangci-lint` image (pinned by
@@ -218,10 +221,13 @@ style conventions are in separate documents:
       `script/docker` and `script/cibuild`; no stage may call `git describe`.
 
 - Every repo should have a Gitea Actions workflow (`.gitea/workflows/`) that
-  runs `script/cibuild` on push. That script runs the gate phases and then the
-  image build, so a successful run means every check passed; a bare
-  `docker build .` does not carry the same guarantee, because its gate phases
-  may come from the cache.
+  runs `script/cibuild` on push, and checks out the repo as its only other step.
+  That script bootstraps, runs the gate phases, and then builds the image, so a
+  successful run means every check passed; a bare `docker build .` does not
+  carry the same guarantee, because its gate phases may come from the cache. The
+  image build is uncached and so runs the gate phases a second time. That is the
+  price of the rule above, and it is worth paying: the image that ships is built
+  from a run of its own gates rather than from a cache entry.
 
 - Use platform-standard formatters: `black` for Python, `prettier` for
   JS/CSS/Markdown/HTML, `go fmt` for Go. Always use default configuration with
@@ -352,7 +358,9 @@ style conventions are in separate documents:
     # trip `set -e`, so the inline form degrades to an empty constant.
     version="$(git describe --tags --always --dirty 2>/dev/null || true)"
     [ -n "$version" ] || version="unknown"
-    docker build --no-cache --build-arg VERSION="$version" .
+    docker build --no-cache \
+        --build-arg VERSION="$version" \
+        -t "$(script/projectname)" .
     ```
 
     `--always` makes an untagged repo yield an abbreviated commit hash rather

script/check

@@ -1,22 +1,16 @@
 #!/bin/sh
-# script/check: run all checks (test, lint, fmt-check) and then the
-# image build. Our own extension to scripts-to-rule-them-all. test and
-# lint are Docker phases; fmt-check is native, because a formatter
-# writes the working tree. Must not modify any files.
+# script/check: run all checks (test, lint, fmt-check). Our own
+# extension to scripts-to-rule-them-all. test and lint are Docker
+# phases; fmt-check is native, because a formatter writes the working
+# tree. Must not modify any files.
 set -eu
 
 SCRIPT_DIR="$(cd "$(dirname "$0")" && pwd -P)"
-ROOT="$(cd "$SCRIPT_DIR/.." && pwd -P)"
 
 main() {
     "$SCRIPT_DIR/test"
     "$SCRIPT_DIR/lint"
     "$SCRIPT_DIR/fmt-check"
-    # No --no-cache here: the two phases this build depends on were just
-    # built uncached above, so what it reuses is that run and not an
-    # older one.
-    cd "$ROOT"
-    docker build -t "$("$SCRIPT_DIR/projectname")" .
 }
 
 main "$@"

script/cibuild

@@ -1,7 +1,10 @@
 #!/bin/sh
-# script/cibuild: run the CI build. script/check runs the gates and
-# builds the image; this repeats the build with the version, which
-# reuses the phases just built rather than re-running them.
+# script/cibuild: run the CI build. It bootstraps first: a CI runner
+# checks out and runs this and nothing else, and script/fmt-check runs
+# the formatter on the host, which a pristine checkout cannot do.
+# --no-cache for the same reason as script/docker: 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 "$0")" && pwd -P)"
@@ -9,6 +12,8 @@ ROOT="$(cd "$SCRIPT_DIR/.." && pwd -P)"
 
 main() {
     cd "$ROOT"
+    "$SCRIPT_DIR/bootstrap"
+    "$SCRIPT_DIR/check"
     # Own line: a failing command substitution inside an argument does
     # not trip `set -e`, so the inline form degrades silently to an
     # empty constant. VERSION is computed here because .dockerignore
@@ -16,8 +21,7 @@ main() {
     # version without failing.
     version="$(git describe --tags --always --dirty 2>/dev/null || true)"
     [ -n "$version" ] || version="unknown"
-    "$SCRIPT_DIR/check"
-    docker build \
+    docker build --no-cache \
         --build-arg VERSION="$version" \
         -t "$("$SCRIPT_DIR/projectname")" .
 }

script/docker

@@ -1,9 +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 this is a standalone entrypoint: the lint and test
-# phases the final stage depends on must run rather than be served from
-# an older build.
+# --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)"