Fold the August fleet findings into the policies, or drop them (closes #62)

Two findings from 2026-08-09 were rules a repository must follow that
`prompts/REPO_POLICIES.md` did not yet state, and are now added where a
reader would look: a new or changed check is proven by planting a defect
it must catch; and a change to a separate workflow limited to `main` by
a `branches` list is first run from the feature branch, added to that
list and removed again before merging. The issue records why every
other finding was dropped. The warning against `golangci-lint config
verify` is dropped because sneak ruled on
#40 (2026-08-10) that there is
no config check step and the config is assumed valid; a vendored
`.golangci.yml` stays byte-identical to the canonical copy.

Model: opus-5-5

.dockerignore

@@ -18,9 +18,16 @@
 # 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.
+# under .git/modules/, nested again for a submodule's own submodules, or in
-.git/config
+# its own .git directory when it keeps one.
-.git/modules/**/config
+# KNOWN GAP: a submodule whose name has a `config` segment (`config`,
+# `deploy/config`, `config/lib`) loses its whole git directory, because
+# `**/.git/modules/**/config` also matches that segment's directory
+# under .git/modules/. Go's version stamping then fails the build;
+# nothing leaks. Name such a submodule without that segment:
+# `git submodule add --name`.
+**/.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.

.gitattributes

@@ -0,0 +1,4 @@
+# Every PR adds an entry at the top of TODO.md's Completed Steps; union keeps
+# both sides instead of conflicting. Git never reports a conflict here: read
+# the merged entries after every merge or rebase.
+TODO.md merge=union

TODO.md

@@ -21,6 +21,34 @@ fmt-check, and commit.
 
 # Completed Steps
 
+- 2026-10-04: Went through the fleet findings recorded on 2026-08-09 (issue 62)
+  and added the two rules `REPO_POLICIES.md` did not yet state: a new or changed
+  check is proven by planting a defect it must catch; and a change to a separate
+  workflow limited to `main` is first run from the feature branch, added to that
+  workflow's `branches` list and removed again before merging. The other
+  findings were already stated, replaced by `--no-cache`, about git worktrees,
+  or about how agents work together. The warning against
+  `golangci-lint config verify` is dropped because sneak ruled on
+  https://git.eeqj.de/sneak/prompts/issues/40 (2026-08-10) that there is no
+  config check step and the config is assumed valid; a vendored `.golangci.yml`
+  stays byte-identical to the canonical copy. The issue gives each reason.
+- 2026-10-04: Added a root `.gitattributes` that merges `TODO.md` with git's
+  union merge (issue 98), so two branches that each add an entry at the top of
+  Completed Steps merge without a conflict. Git now never reports a conflict in
+  `TODO.md`: a real conflict elsewhere keeps both versions of the line, and when
+  two new entries share an identical line, one is inserted into the middle of
+  the other, which a rebase can do to an entry already on `next`. Read the
+  merged entries after every merge or rebase. This applies to this repository
+  only; no canonical file changed.
+- 2026-10-04: The canonical `.dockerignore` now also keeps out the git `config`
+  of a submodule that keeps its own `.git` directory, which still reached the
+  image (issue 88): both git patterns now carry the `**/` prefix. A submodule
+  whose name has a `config` segment (`config`, `deploy/config`, `config/lib`)
+  still loses its whole git directory, so Go's version stamping fails the build;
+  the file records this as a `KNOWN GAP:` with the remedy,
+  `git submodule add --name`. Closing it would take a wildcard re-include, which
+  makes BuildKit walk every excluded directory, such as `node_modules`, on every
+  build. `REPO_POLICIES.md` and both checklists say so in the same words.
 - 2026-10-04: The note under the canonical Go `Dockerfile` example in
   `REPO_POLICIES.md` now installs lint-phase system libraries with `apt-get`
   under their Debian package names (issue 83). The `golangci/golangci-lint`

prompts/EXISTING_REPO_CHECKLIST.md

@@ -63,10 +63,15 @@ 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` and each submodule's
+      the build context. It keeps out every git `config` at any depth
-      `config` under `.git/modules/` at any depth (`.git/modules/**/config`),
+      (`**/.git/config`, `**/.git/modules/**/config`): the repository's own,
-      which `git describe` does not need and which can hold a credential: a
+      each submodule's under `.git/modules/`, and that of a submodule keeping
-      password in a remote URL, or the token the CI checkout step stores there.
+      its own `.git` directory. `git describe` does not need them, and each can
+      hold a credential: a password in a remote URL, or the token the CI
+      checkout step stores there. A submodule whose name has a `config` segment
+      (`config`, `deploy/config`, `config/lib`) loses its whole git directory to
+      `**/.git/modules/**/config`, and Go's version stamping then fails the
+      build: give it a name without that segment (`git submodule add --name`).
       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

prompts/NEW_REPO_CHECKLIST.md

@@ -71,10 +71,15 @@ 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` and each submodule's
+      into the build context. It keeps out every git `config` at any depth
-      `config` under `.git/modules/` at any depth (`.git/modules/**/config`),
+      (`**/.git/config`, `**/.git/modules/**/config`): the repository's own,
-      which `git describe` does not need and which can hold a credential: a
+      each submodule's under `.git/modules/`, and that of a submodule keeping
-      password in a remote URL, or the token the CI checkout step stores there.
+      its own `.git` directory. `git describe` does not need them, and each can
+      hold a credential: a password in a remote URL, or the token the CI
+      checkout step stores there. A submodule whose name has a `config` segment
+      (`config`, `deploy/config`, `config/lib`) loses its whole git directory to
+      `**/.git/modules/**/config`, and Go's version stamping then fails the
+      build: give it a name without that segment (`git submodule add --name`).
       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

prompts/REPO_POLICIES.md

@@ -156,6 +156,9 @@ style conventions are in separate documents:
   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.
+  When a check is added or changed, prove it works by planting a defect it must
+  catch and watching the run fail on it, then revert the defect. A green run
+  alone shows neither that the check ran nor that it covers what it should.
 
 - **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
@@ -248,11 +251,16 @@ style conventions are in separate documents:
             && rm -rf /var/lib/apt/lists/*
         ```
 
-    - `.dockerignore` lets `.git` into the build context. It keeps out
+    - `.dockerignore` lets `.git` into the build context. It keeps out every git
-      `.git/config` and each submodule's `config` under `.git/modules/` at any
+      `config` at any depth (`**/.git/config`, `**/.git/modules/**/config`): the
-      depth (`.git/modules/**/config`), which `git describe` does not need and
+      repository's own, each submodule's under `.git/modules/`, and that of a
-      which can hold a credential: a password in a remote URL, or the token the
+      submodule keeping its own `.git` directory. `git describe` does not need
-      CI checkout step stores there. The stage that compiles has `git` (the
+      them, and each can hold a credential: a password in a remote URL, or the
+      token the CI checkout step stores there. A submodule whose name has a
+      `config` segment (`config`, `deploy/config`, `config/lib`) loses its whole
+      git directory to `**/.git/modules/**/config`, and Go's version stamping
+      then fails the build: give it a name without that segment
+      (`git submodule add --name`). 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
@@ -274,7 +282,12 @@ style conventions are in separate documents:
   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.
+  from a run of its own gates rather than from a cache entry. A separate
+  workflow limited to `main` by a `branches` list under `on: push` cannot be
+  checked by review: to try a change to it, add the feature branch to that list
+  and push, then remove the branch from the list again before merging. Keep any
+  job in it that publishes behind `if: github.ref_name == 'main'`, so the run
+  from the feature branch publishes nothing.
 
 - Use platform-standard formatters: `black` for Python, `prettier` for
   JS/CSS/Markdown/HTML, `go fmt` for Go. Always use default configuration with