Derive the image version from git; send .git without its config (closes #69, closes #71)

The canonical documents told every repo to exclude .git from the build
context, default ARG VERSION to dev and never run git describe in a
build stage, so an image built from a clone with no build argument
reported dev. .dockerignore now sends .git but keeps out .git/config,
which can hold a credential. The Dockerfile example installs git, takes
the VERSION build argument when one is given and otherwise
git describe --tags --always, and fails when .git exists but the version
is empty, dev or unknown. The policy and both checklists state the rule
in the same words, including that a plain docker build . with no build
arguments must succeed.

Model: opus-5-5

.gitignore

@@ -20,26 +20,8 @@ Thumbs.db
 # Node
 node_modules/
 
-# Secrets. Unanchored like every entry above, so each matches at every
-# depth. Matching is case-sensitive on Linux, so names use character
-# ranges rather than a lowercase form that misses `Server.Key`.
-
-# Environment files. `*.env` covers bare `.env` and the `prod.env`
-# convention. Only the templates `example.env` and `sample.env` are
-# re-included below. A repository that commits any other template adds
-# its own negation after these lines, for example `!.env.example`.
-*.[eE][nN][vV]
-.[eE][nN][vV].*
-.[eE][nN][vV][rR][cC]
-!example.env
-!sample.env
-
-# Private keys and the bundles carrying them.
-*.[pP][eE][mM]
-*.[kK][eE][yY]
-*.[pP]12
-*.[pP][fF][xX]
-[iI][dD]_[rR][sS][aA]
-[iI][dD]_[dD][sS][aA]
-[iI][dD]_[eE][cC][dD][sS][aA]
-[iI][dD]_[eE][dD]25519
+# Environment / secrets
+.env
+.env.*
+*.pem
+*.key

TODO.md

@@ -21,18 +21,6 @@ fmt-check, and commit.
 
 # Completed Steps
 
-- 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.
-  The stage that compiles runs `git config --system --add safe.directory /src`,
-  because a context sent as a tar stream keeps the sender's file owners and git
-  refuses that checkout, leaving the version empty. Both checklists state that
-  step in the same words.
-- 2026-10-03: Brought the canonical `.gitignore` level with `.dockerignore` on
-  secrets (issue 38): it now also ignores `prod.env`-style `*.env` files,
-  `.envrc`, `*.p12`, `*.pfx` and the extensionless SSH private keys, written to
-  `.gitignore`'s own rules (no `**/` prefix) and case-folded with character
-  ranges. `example.env` and `sample.env` stay trackable through negations.
 - 2026-10-02: The image version now comes from git inside the build (issues 69
   and 71), superseding the 2026-09-08 entry that excluded `.git`. The canonical
   `.dockerignore` sends `.git` but keeps out `.git/config`, which can hold a

prompts/EXISTING_REPO_CHECKLIST.md

@@ -1,6 +1,6 @@
 ---
 title: Existing Repo Checklist
-last_modified: 2026-10-03
+last_modified: 2026-10-02
 ---
 
 Use this checklist when beginning work in a repo that may not yet conform to our
@@ -67,14 +67,10 @@ with your task.
       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
+      the short commit when no tag is reachable. `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

prompts/NEW_REPO_CHECKLIST.md

@@ -1,6 +1,6 @@
 ---
 title: New Repo Checklist
-last_modified: 2026-10-03
+last_modified: 2026-10-02
 ---
 
 Use this checklist when creating a new repository from scratch. Follow the steps
@@ -76,14 +76,10 @@ Template files can be fetched from:
       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
+      the short commit when no tag is reachable. `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

prompts/REPO_POLICIES.md

@@ -1,6 +1,6 @@
 ---
 title: Repository Policies
-last_modified: 2026-10-03
+last_modified: 2026-10-02
 ---
 
 This document covers repository structure, tooling, and workflow standards. Code
@@ -160,7 +160,7 @@ style conventions are in separate documents:
 - **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
   hash), so lint failures surface in seconds rather than after a full compile,
-  and the test phase is based on the Debian Go image. The canonical Go repo
+  and the test phase is based on the Go image. The canonical Go repo
   `Dockerfile`:
 
     ```dockerfile
@@ -173,9 +173,8 @@ style conventions are in separate documents:
     COPY . .
     RUN golangci-lint run --config .golangci.yml ./...
 
-    # Test phase. -race needs cgo and so a C compiler, which the Debian Go
-    # image ships and the alpine one does not.
-    # golang:1.x, YYYY-MM-DD
+    # Test phase
+    # golang:1.x-alpine, YYYY-MM-DD
     FROM golang@sha256:... AS test
     WORKDIR /src
     COPY go.mod go.sum ./
@@ -193,8 +192,6 @@ style conventions are in separate documents:
     COPY --from=lint /src/go.sum /dev/null
     COPY --from=test /src/go.sum /dev/null
     RUN apk add --no-cache git
-    # A tar-stream context keeps the sender's file owners, which git refuses.
-    RUN git config --system --add safe.directory /src
     WORKDIR /src
     COPY go.mod go.sum ./
     RUN go mod download
@@ -247,14 +244,11 @@ style conventions are in separate documents:
       `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.
+      reachable. `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.
 
 - Every repo should have a Gitea Actions workflow (`.gitea/workflows/`) that
   runs `script/cibuild` on push, and checks out the repo as its only other step.