Keep each submodule's git config out of the build context (closes #75)

The canonical `.dockerignore` kept out `.git/config`, which can hold a credential, but not the `config` in each submodule's git directory under `.git/modules/`, nested again for a submodule's own submodules. It now also lists `.git/modules/**/config`, with one sentence in the comment above; `prompts/REPO_POLICIES.md` and both checklists say so in the same words.

The pattern stays under `.git/modules/` because `.git/**/config` would also drop a branch or tag named `config`, which `git describe` may need.

Known gap: a submodule whose name has a `config` path segment loses its whole git directory, so Go's version stamping fails the build loudly; tracked separately.

Model: opus-5-5

.dockerignore

@@ -17,7 +17,10 @@
 # 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.
+# Each submodule keeps a config with the same exposure in its git directory
+# under .git/modules/, nested again for a submodule's own submodules.
 .git/config
+.git/modules/**/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.

TODO.md

@@ -21,12 +21,12 @@ fmt-check, and commit.
 
 # Completed Steps
 
-- 2026-10-04: Rewrote the note under the canonical Go `make test` example in
-  `REPO_POLICIES.md` (issue 77), which still named the cache-busting build
-  argument that `--no-cache` replaced. It now says where Go's test result cache
-  can replay a pass: on a developer's machine, where the Makefile target runs,
-  and not in the `test` phase of the `Dockerfile`, whose base image and earlier
-  steps hold no result for the repo's tests.
+- 2026-10-04: The canonical `.dockerignore` now also keeps out each submodule's
+  `config` (issue 75). A submodule's git directory lives under `.git/modules/`,
+  nested again for its own submodules, and its `config` can hold a credential
+  just like `.git/config`. The pattern `.git/modules/**/config` covers every
+  depth and leaves the top-level `.git` that `git describe` reads untouched.
+  `REPO_POLICIES.md` and both checklists say so in the same words.
 - 2026-10-03: Fixed two defects in the canonical Go `Dockerfile` example (issue
   73). The test phase now uses the Debian Go image, since `-race` needs cgo and
   the alpine image has no C compiler, so the phase failed before running a test.

prompts/EXISTING_REPO_CHECKLIST.md

@@ -1,6 +1,6 @@
 ---
 title: Existing Repo Checklist
-last_modified: 2026-10-03
+last_modified: 2026-10-04
 ---
 
 Use this checklist when beginning work in a repo that may not yet conform to our
@@ -59,26 +59,28 @@ with your task.
       here run anywhere other than the repo root, the anchored entry misses
       `services/api/.claude/`: add anchored entries for those directories.
 - [ ] If the repo embeds a version in a binary: `.dockerignore` lets `.git` into
-      the build context. It keeps out `.git/config`, which `git describe` does
-      not need and which can hold a credential: a password in a remote URL, or
-      the token the CI checkout step stores there. The stage that compiles has
-      `git` (the Debian Go image has it; an alpine one needs
-      `apk add --no-cache git`) and takes the version from the `VERSION` build
-      argument when one is given, otherwise from `git describe --tags --always`.
-      That gives the tag on a tagged commit; on a later commit, the tag, the
-      number of commits since it and the short commit (`v1.2.3-4-gabc1234`); and
-      the short commit when no tag is reachable. The stage that compiles also
-      marks its working directory safe for git
-      (`git config --system --add safe.directory /src`): a context sent as a tar
-      stream keeps the sender's file owners, and git refuses a checkout owned by
-      another user, so the version would come out empty. `ARG VERSION` has no
-      default, and the build fails if the context carries `.git` and the version
-      still comes out empty, `dev` or `unknown`. A plain `docker build .` with
-      no build arguments must succeed; a Dockerfile that refuses an empty build
-      argument drops that refusal and keeps the argument. `script/docker` and
-      `script/cibuild` pass the version they compute on the host; it takes
-      precedence. A tag-derived version additionally needs `fetch-depth: 0` on
-      the CI checkout step, which clones shallow and fetches no tags by default.
+      the build context. It keeps out `.git/config` and each submodule's
+      `config` under `.git/modules/` at any depth (`.git/modules/**/config`),
+      which `git describe` does not need and which can hold a credential: a
+      password in a remote URL, or the token the CI checkout step stores there.
+      The stage that compiles has `git` (the Debian Go image has it; an alpine
+      one needs `apk add --no-cache git`) and takes the version from the
+      `VERSION` build argument when one is given, otherwise from
+      `git describe --tags --always`. That gives the tag on a tagged commit; on
+      a later commit, the tag, the number of commits since it and the short
+      commit (`v1.2.3-4-gabc1234`); and the short commit when no tag is
+      reachable. The stage that compiles also marks its working directory safe
+      for git (`git config --system --add safe.directory /src`): a context sent
+      as a tar stream keeps the sender's file owners, and git refuses a checkout
+      owned by another user, so the version would come out empty. `ARG VERSION`
+      has no default, and the build fails if the context carries `.git` and the
+      version still comes out empty, `dev` or `unknown`. A plain
+      `docker build .` with no build arguments must succeed; a Dockerfile that
+      refuses an empty build argument drops that refusal and keeps the argument.
+      `script/docker` and `script/cibuild` pass the version they compute on the
+      host; it takes precedence. A tag-derived version additionally needs
+      `fetch-depth: 0` on the CI checkout step, which clones shallow and fetches
+      no tags by default.
 - [ ] Gitea Actions workflow in `.gitea/workflows/` runs `script/cibuild` on
       push — reference
       `https://git.eeqj.de/sneak/prompts/raw/branch/main/.gitea/workflows/check.yml`

prompts/NEW_REPO_CHECKLIST.md

@@ -1,6 +1,6 @@
 ---
 title: New Repo Checklist
-last_modified: 2026-10-03
+last_modified: 2026-10-04
 ---
 
 Use this checklist when creating a new repository from scratch. Follow the steps
@@ -68,23 +68,24 @@ Template files can be fetched from:
       will run them in subdirectories, `services/api/.claude/` needs its own
       anchored entry.
     - If the image embeds a version in a binary: `.dockerignore` lets `.git`
-      into the build context. It keeps out `.git/config`, which `git describe`
-      does not need and which can hold a credential: a password in a remote URL,
-      or the token the CI checkout step stores there. The stage that compiles
-      has `git` (the Debian Go image has it; an alpine one needs
-      `apk add --no-cache git`) and takes the version from the `VERSION` build
-      argument when one is given, otherwise from `git describe --tags --always`.
-      That gives the tag on a tagged commit; on a later commit, the tag, the
-      number of commits since it and the short commit (`v1.2.3-4-gabc1234`); and
-      the short commit when no tag is reachable. The stage that compiles also
-      marks its working directory safe for git
-      (`git config --system --add safe.directory /src`): a context sent as a tar
-      stream keeps the sender's file owners, and git refuses a checkout owned by
-      another user, so the version would come out empty. `ARG VERSION` has no
-      default, and the build fails if the context carries `.git` and the version
-      still comes out empty, `dev` or `unknown`. A plain `docker build .` with
-      no build arguments must succeed; a Dockerfile that refuses an empty build
-      argument drops that refusal and keeps the argument.
+      into the build context. It keeps out `.git/config` and each submodule's
+      `config` under `.git/modules/` at any depth (`.git/modules/**/config`),
+      which `git describe` does not need and which can hold a credential: a
+      password in a remote URL, or the token the CI checkout step stores there.
+      The stage that compiles has `git` (the Debian Go image has it; an alpine
+      one needs `apk add --no-cache git`) and takes the version from the
+      `VERSION` build argument when one is given, otherwise from
+      `git describe --tags --always`. That gives the tag on a tagged commit; on
+      a later commit, the tag, the number of commits since it and the short
+      commit (`v1.2.3-4-gabc1234`); and the short commit when no tag is
+      reachable. The stage that compiles also marks its working directory safe
+      for git (`git config --system --add safe.directory /src`): a context sent
+      as a tar stream keeps the sender's file owners, and git refuses a checkout
+      owned by another user, so the version would come out empty. `ARG VERSION`
+      has no default, and the build fails if the context carries `.git` and the
+      version still comes out empty, `dev` or `unknown`. A plain
+      `docker build .` with no build arguments must succeed; a Dockerfile that
+      refuses an empty build argument drops that refusal and keeps the argument.
     - The Dockerfile carries a `lint` phase and a `test` phase, each invoking
       its tool directly rather than through `make` or `script/`, and the final
       stage carries a `COPY --from=` of a harmless file from each so the image

prompts/REPO_POLICIES.md

@@ -239,20 +239,21 @@ style conventions are in separate documents:
     - If the project requires CGO or system libraries for linting (e.g.
       `vips-dev`), install them in the lint phase with `apk add`.
     - `.dockerignore` lets `.git` into the build context. It keeps out
-      `.git/config`, which `git describe` does not need and which can hold a
-      credential: a password in a remote URL, or the token the CI checkout step
-      stores there. The stage that compiles has `git` (the Debian Go image has
-      it; an alpine one needs `apk add --no-cache git`) and takes the version
-      from the `VERSION` build argument when one is given, otherwise from
-      `git describe --tags --always`. That gives the tag on a tagged commit; on
-      a later commit, the tag, the number of commits since it and the short
-      commit (`v1.2.3-4-gabc1234`); and the short commit when no tag is
-      reachable. The stage that compiles also marks its working directory safe
-      for git (`git config --system --add safe.directory /src`): a context sent
-      as a tar stream keeps the sender's file owners, and git refuses a checkout
-      owned by another user, so the version would come out empty. `ARG VERSION`
-      has no default, and the build fails if the context carries `.git` and the
-      version still comes out empty, `dev` or `unknown`. A plain
+      `.git/config` and each submodule's `config` under `.git/modules/` at any
+      depth (`.git/modules/**/config`), which `git describe` does not need and
+      which can hold a credential: a password in a remote URL, or the token the
+      CI checkout step stores there. The stage that compiles has `git` (the
+      Debian Go image has it; an alpine one needs `apk add --no-cache git`) and
+      takes the version from the `VERSION` build argument when one is given,
+      otherwise from `git describe --tags --always`. That gives the tag on a
+      tagged commit; on a later commit, the tag, the number of commits since it
+      and the short commit (`v1.2.3-4-gabc1234`); and the short commit when no
+      tag is reachable. The stage that compiles also marks its working directory
+      safe for git (`git config --system --add safe.directory /src`): a context
+      sent as a tar stream keeps the sender's file owners, and git refuses a
+      checkout owned by another user, so the version would come out empty.
+      `ARG VERSION` has no default, and the build fails if the context carries
+      `.git` and the version still comes out empty, `dev` or `unknown`. A plain
       `docker build .` with no build arguments must succeed; a Dockerfile that
       refuses an empty build argument drops that refusal and keeps the argument.
 
@@ -316,19 +317,17 @@ style conventions are in separate documents:
     ```
 
     `-count=1` is required on both invocations: it defeats Go's test _result_
-    cache, so neither run can report a stored pass in place of running the
-    tests. It leaves the build cache alone, so it costs the runtime of the suite
-    and no recompilation.
+    cache, so the target cannot report a pass it did not earn, and the rerun
+    reproduces a failure instead of replaying it. It leaves the build cache
+    alone, so it costs the runtime of the suite and no recompilation.
 
-    That cache is Go's own, separate from Docker's layer cache. Go stores a
-    passing result in its cache directory (`GOCACHE`), and when the same tests
-    run again on unchanged code it prints that result, marked `(cached)`,
-    without running them. That matters on a developer's machine, where this
-    target runs and the directory lasts from one run to the next. The `test`
-    phase of the `Dockerfile` needs no `-count=1`: its base image holds no
-    result for this repo's tests and nothing before its `go test` step runs a
-    test, so there is nothing to replay. `--no-cache` (above) is what makes that
-    step run on an unchanged tree.
+    Note that this is a second, independent cache, stacked below the Docker
+    layer cache that [issue #26](https://git.eeqj.de/sneak/prompts/issues/26)
+    addresses. `CHECK_EPOCH` guarantees the `RUN make test` _step_ re-executes;
+    it does not guarantee `go test` inside that step does any work, because the
+    `GOCACHE` baked into earlier image layers survives into the re-executed
+    step. They are two separate defects requiring two separate fixes, and a fix
+    for one must not be recorded as covering the other.
 
     Python example: