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

.dockerignore

@@ -13,9 +13,11 @@
 # `/myapp`, never `**/myapp`, which also matches `cmd/myapp/` and
 # deletes the package directory from the context.
 
-# Excluding .git means `git describe` cannot run in any build stage and
-# fails quietly there; pass the version in with --build-arg VERSION.
-.git
+# .git is sent without its config. Without a VERSION build argument the
+# 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.
+.git/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.

Dockerfile

@@ -52,7 +52,8 @@ RUN script/bootstrap
 
 COPY . .
 
-# The version is computed on the host and passed in, because
-# .dockerignore excludes .git.
-ARG VERSION=dev
+# Nothing here is compiled and a LABEL cannot run git, so the version is
+# the VERSION build argument that script/docker and script/cibuild pass;
+# a plain `docker build .` leaves it empty.
+ARG VERSION
 LABEL org.opencontainers.image.version="${VERSION}"

README.md

@@ -132,8 +132,7 @@ alpine. We provide:
   `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/fmt-check` is native)
 - `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

@@ -21,6 +21,15 @@ fmt-check, and commit.
 
 # Completed Steps
 
+- 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
+  credential. The Dockerfile example in `REPO_POLICIES.md` 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`; a plain `docker build .` with no build arguments
+  must succeed. This repo's `script/docker` and `script/cibuild` still pass
+  `--build-arg VERSION`, since its own `Dockerfile` compiles nothing.
 - 2026-09-08: Moved linting and testing into Docker as phases of the main
   `Dockerfile`, per the owner ruling on issue 40. `script/lint` and
   `script/test` build one phase each by name with `--no-cache` — the same answer

prompts/CODE_STYLEGUIDE_GO.md

@@ -1,6 +1,6 @@
 ---
 title: Code Styleguide — Go
-last_modified: 2026-09-08
+last_modified: 2026-10-02
 ---
 
 1.  Try to hard wrap long lines at 77 characters or less.
@@ -48,14 +48,11 @@ last_modified: 2026-09-08
     ```
 
     ```make
-    # ?= rather than := because this `$(shell git describe ...)` is only
-    # correct on the host: `.dockerignore` excludes `.git`, so evaluated
-    # inside a build stage it expands to the empty string without failing
-    # and the binary reports no version. The version is computed on the
-    # host by `script/docker` / `script/cibuild` and passed with
-    # `--build-arg VERSION=...`; where a build stage invokes make,
-    # `ARG VERSION` puts it in the environment and `?=` defers to it.
-    VERSION ?= $(shell git describe --always --dirty)
+    # ?= rather than := so that a `VERSION` build argument takes precedence:
+    # where a build stage invokes make, `ARG VERSION` puts it in the
+    # environment and `?=` defers to it. Otherwise `git describe` runs, in a
+    # build stage on the `.git` the build context carries.
+    VERSION ?= $(shell git describe --tags --always)
 
     GOLDFLAGS += -X main.Version=$(VERSION)
 

prompts/EXISTING_REPO_CHECKLIST.md

@@ -1,6 +1,6 @@
 ---
 title: Existing Repo Checklist
-last_modified: 2026-09-08
+last_modified: 2026-10-02
 ---
 
 Use this checklist when beginning work in a repo that may not yet conform to our
@@ -44,7 +44,7 @@ with your task.
       `script/test` — those are themselves a `docker build` and would recurse
       inside a build step
 - [ ] Every depth-independent pattern in `.dockerignore` carries a `**/` prefix,
-      only genuinely root-anchored entries such as `.git` are unprefixed, and
+      only genuinely root-anchored entries such as `.claude` are unprefixed, and
       `.gitignore`'s patterns have not been transplanted unmodified — the
       transplanted form leaves `config/.env` and `certs/server.key` in the build
       context while reading as solved
@@ -58,11 +58,23 @@ with your task.
       can copy another session's unreviewed work into an image layer. If agents
       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, that version is computed on the
-      host and passed with `--build-arg VERSION=...` by `script/docker` and
-      `script/cibuild`, and no stage calls `git describe`. A tag-derived version
-      additionally needs `fetch-depth: 0` on the CI checkout step, which clones
-      shallow and fetches no tags by default.
+- [ ] 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. `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/GO_HTTP_SERVER_CONVENTIONS.md

@@ -1,6 +1,6 @@
 ---
 title: Go HTTP Server Conventions
-last_modified: 2026-09-08
+last_modified: 2026-10-02
 ---
 
 This document defines the architectural patterns, design decisions, and
@@ -984,13 +984,10 @@ func main() {
 Use ldflags to inject version information at build time:
 
 ```makefile
-# ?= rather than := because this `$(shell git describe ...)` is only correct
-# on the host: `.dockerignore` excludes `.git`, so evaluated inside a build
-# stage it expands to the empty string without failing and the binary reports
-# no version. The version is computed on the host by `script/docker` /
-# `script/cibuild` and passed with `--build-arg VERSION=...`; where the build
-# stage invokes make, `ARG VERSION` puts it in the environment and `?=` defers
-# to it.
+# ?= rather than := so that a `VERSION` build argument takes precedence:
+# where a build stage invokes make, `ARG VERSION` puts it in the
+# environment and `?=` defers to it. Otherwise `git describe` runs, in a
+# build stage on the `.git` the build context carries.
 VERSION ?= $(shell git describe --tags --always)
 
 build:

prompts/NEW_REPO_CHECKLIST.md

@@ -1,6 +1,6 @@
 ---
 title: New Repo Checklist
-last_modified: 2026-09-08
+last_modified: 2026-10-02
 ---
 
 Use this checklist when creating a new repository from scratch. Follow the steps
@@ -67,11 +67,20 @@ Template files can be fetched from:
       note that it only covers agents running at the repo root — if this repo
       will run them in subdirectories, `services/api/.claude/` needs its own
       anchored entry.
-    - If the image embeds a version in a binary, the version is computed on the
-      host and passed with `--build-arg VERSION=...`, and `ARG VERSION=dev` is
-      declared in the stage that compiles. **No stage calls `git describe`** —
-      `.dockerignore` excludes `.git`, so it yields an empty version without
-      failing the build.
+    - 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. `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

@@ -1,6 +1,6 @@
 ---
 title: Repository Policies
-last_modified: 2026-09-08
+last_modified: 2026-10-02
 ---
 
 This document covers repository structure, tooling, and workflow standards. Code
@@ -191,15 +191,27 @@ style conventions are in separate documents:
     FROM golang@sha256:... AS builder
     COPY --from=lint /src/go.sum /dev/null
     COPY --from=test /src/go.sum /dev/null
+    RUN apk add --no-cache git
     WORKDIR /src
     COPY go.mod go.sum ./
     RUN go mod download
     COPY . .
 
-    ARG VERSION=dev
-    RUN CGO_ENABLED=0 go build -trimpath \
-        -ldflags="-s -w -X main.Version=${VERSION}" \
-        -o /app ./cmd/app/
+    # The VERSION build arg when one is given, otherwise
+    # `git describe --tags --always` on the .git in the build context. With
+    # .git present, a version that is still empty, dev or unknown fails the
+    # build: git is missing or could not read the checkout.
+    ARG VERSION
+    RUN VERSION="${VERSION:-$(git describe --tags --always)}"; \
+        if [ -e .git ]; then \
+            case "$VERSION" in ""|dev|unknown) \
+                echo "version is '$VERSION' although .git is present" >&2; \
+                exit 1 ;; \
+            esac; \
+        fi; \
+        CGO_ENABLED=0 go build -trimpath \
+            -ldflags="-s -w -X main.Version=${VERSION}" \
+            -o /app ./cmd/app/
 
     # Runtime stage, and the last one
     FROM alpine@sha256:...
@@ -223,8 +235,20 @@ style conventions are in separate documents:
       `RUN mkdir -p web/dist && touch web/dist/index.html web/dist/style.css`.
     - If the project requires CGO or system libraries for linting (e.g.
       `vips-dev`), install them in the lint phase with `apk add`.
-    - `ARG VERSION=dev` is declared in the stage that compiles and supplied by
-      `script/docker` and `script/cibuild`; no stage may call `git describe`.
+    - `.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. `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.
@@ -340,7 +364,7 @@ style conventions are in separate documents:
   — which is more dangerous than a short file with no secret patterns at all,
   because it reads as solved and stops anyone looking. Give every
   depth-independent pattern the `**/` prefix and leave only genuinely
-  root-anchored entries unprefixed: `.git`, and the repo's own host-built
+  root-anchored entries unprefixed: `.claude`, and the repo's own host-built
   binary, written `/myapp` and never `**/myapp`, which would also match
   `cmd/myapp/` and delete the package directory from the context. Matching is
   case-sensitive, and an ALL-CAPS twin per pattern still misses `Server.Key`, so
@@ -365,12 +389,13 @@ style conventions are in separate documents:
   directory, so a repo running agents in subdirectories still ships
   `services/api/.claude/` and must add its own anchored entry there.
 
-- **Excluding `.git` means `git describe` cannot run inside any build stage, and
-  it fails quietly there.** In a build stage there is no repository, so
-  `git describe` writes nothing to stdout, `-X main.Version=` comes out empty,
-  the binary reports no version at all, and the build still exits 0. Compute the
-  version on the host and thread it in as a build arg. `script/docker` and
-  `script/cibuild` do this, byte-identically across repos:
+- **A plain `docker build .` of a clone stamps the version that
+  `git describe --tags --always` gives**, derived from the `.git` in the build
+  context as the canonical `Dockerfile` above shows. Without its failure check,
+  a missing `git` or an unreadable checkout would leave `-X main.Version=` empty
+  and the build would still exit 0. `script/docker` and `script/cibuild` pass
+  the version they compute on the host; it takes precedence. They do this
+  byte-identically across repos:
 
     ```sh
     # Own line: a failing command substitution inside an argument does not
@@ -387,7 +412,7 @@ style conventions are in separate documents:
     fallback is applied — a live check that fires on a build from an export with
     no `.git` and on a repository with no commits yet. Do not fold it into the
     substitution as `|| echo unknown`, which makes the guard unreachable. The
-    Dockerfile's side is `ARG VERSION=dev` in the stage that compiles, declared
+    Dockerfile's side is `ARG VERSION` in the stage that compiles, declared
     there because `ARG` is stage-scoped; passing `VERSION` to a repo whose
     Dockerfile declares no such `ARG` is ignored and costs nothing, which is why
     the scripts stay byte-identical. One consequence for CI: the standard

script/cibuild

@@ -16,9 +16,8 @@ main() {
     "$SCRIPT_DIR/check"
     # Own line: a failing command substitution inside an argument does
     # not trip `set -e`, so the inline form degrades silently to an
-    # empty constant. VERSION is computed here because .dockerignore
-    # excludes .git, so `git describe` in a build stage yields an empty
-    # version without failing.
+    # empty constant. The VERSION build argument takes precedence over
+    # the version a build stage derives from the .git in the context.
     version="$(git describe --tags --always --dirty 2>/dev/null || true)"
     [ -n "$version" ] || version="unknown"
     docker build --no-cache \

script/docker

@@ -12,9 +12,8 @@ main() {
     cd "$ROOT"
     # Own line: a failing command substitution inside an argument does
     # not trip `set -e`, so the inline form degrades silently to an
-    # empty constant. VERSION is computed here because .dockerignore
-    # excludes .git, so `git describe` in a build stage yields an empty
-    # version without failing.
+    # empty constant. The VERSION build argument takes precedence over
+    # the version a build stage derives from the .git in the context.
     version="$(git describe --tags --always --dirty 2>/dev/null || true)"
     [ -n "$version" ] || version="unknown"
     docker build --no-cache \