ci: call the shared build-image script instead of an inline copy (infra#309)

Wave 2. The buildctl/skopeo step here was one of nineteen near-identical
copies; the implementation now lives in .gitea/build-image.sh,
byte-identical to mathias/infra's ci-templates/build-image.sh and held
there by a drift gate. Labels, tags and build-args are inputs.

Behaviour unchanged: same registry, same :sha/:latest/version tags, same
revision and source labels.

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_011PL5XcG68SvQqz3vGVbWbf

.gitea/build-image.sh

@@ -0,0 +1,121 @@
+#!/usr/bin/env bash
+# Build an OCI image with buildctl and push it to the local registry.
+#
+# CANONICAL COPY: mathias/infra ci-templates/build-image.sh (infra#309).
+# Every repo carries a byte-identical copy at .gitea/build-image.sh, written by
+# `task ci:sync` and held in place by the drift gate. DO NOT EDIT THE COPIES --
+# edit here, re-sync, and the gate will tell you which repos still disagree.
+#
+# Why this exists: this step was hand-copied into a dozen repos, so migrating it
+# off rootless buildah (infra#241) meant eleven near-identical commits, eleven
+# verifications, and three separate rediscoveries of the same fix in the two
+# repo templates and the gitea-ci skill. The differences between the copies were
+# incidental -- a label here, a build-arg there -- never intentional. Those are
+# inputs now, not forks of the implementation.
+#
+# Why buildctl and not buildah: the gitea-runner pod runs with
+# `capabilities: drop [ALL]` and `allowPrivilegeEscalation: false`, which
+# unconditionally blocks the setuid-root exec that rootless buildah's uid/gid
+# remapping needs, and the pod has no OCI runtime at all. buildctl is a thin
+# client -- it hands the build to the host's buildkitd over a socket, so the
+# privileged layer work happens on the host and this pod's securityContext is
+# not in the picture. buildah is absent from the runner image as of baked-v14
+# and its absence is asserted at pod start (infra#308).
+#
+# Inputs, all via environment:
+#
+#   IMAGE            (required) image name, e.g. cobalt-dingo
+#   REGISTRY         default localhost:5000
+#   SHA_TAG          default `git rev-parse --short HEAD`
+#   VERSION_TAG      optional extra tag, e.g. v1.2.3 on a tag build
+#   PUSH_LATEST      default 1; set 0 to skip the :latest tag
+#   CONTEXT          default . -- build context directory
+#   DOCKERFILE_DIR   default $CONTEXT -- directory holding the Dockerfile
+#   DOCKERFILE_NAME  optional, when the file is not named `Dockerfile`
+#   TARGET           optional, multi-stage build target (--opt target=)
+#   BUILD_ARGS       optional, space-separated K=V pairs
+#   BUILD_SECRETS    optional, space-separated buildkit secret specs, each
+#                    `id=NAME,src=PATH`. Pass the SPEC only -- the caller
+#                    writes the secret to PATH itself. A secret VALUE must
+#                    never be passed here: it would land in this script's
+#                    argv and therefore in the CI log.
+#   EXTRA_LABELS     optional, space-separated K=V pairs
+#   GIT_SHA          optional, stamped as org.opencontainers.image.revision
+#   IMAGE_SOURCE     optional, stamped as org.opencontainers.image.source
+#
+# Note on shell style below: every conditional is a full `if` block, never
+# `[ -n "$X" ] && cmd`. Under `set -e` the && form exits the script whenever the
+# test is false, which is a real bug this estate has already shipped once.
+
+set -euo pipefail
+
+if [ -z "${IMAGE:-}" ]; then
+  echo "build-image: IMAGE is required" >&2
+  exit 2
+fi
+
+REGISTRY="${REGISTRY:-localhost:5000}"
+BUILDKIT_HOST="${BUILDKIT_HOST:-unix:///run/buildkit/buildkitd.sock}"
+CONTEXT="${CONTEXT:-.}"
+DOCKERFILE_DIR="${DOCKERFILE_DIR:-$CONTEXT}"
+PUSH_LATEST="${PUSH_LATEST:-1}"
+VERSION_TAG="${VERSION_TAG:-}"
+
+if [ -z "${SHA_TAG:-}" ]; then
+  SHA_TAG="$(git rev-parse --short HEAD)"
+fi
+
+REF="${REGISTRY}/${IMAGE}:${SHA_TAG}"
+
+TAR_FILE="$(mktemp)"
+trap 'rm -f "$TAR_FILE"' EXIT
+
+args=(
+  --frontend dockerfile.v0
+  --local "context=${CONTEXT}"
+  --local "dockerfile=${DOCKERFILE_DIR}"
+)
+
+if [ -n "${DOCKERFILE_NAME:-}" ]; then
+  args+=(--opt "filename=${DOCKERFILE_NAME}")
+fi
+if [ -n "${TARGET:-}" ]; then
+  args+=(--opt "target=${TARGET}")
+fi
+for spec in ${BUILD_SECRETS:-}; do
+  # Opaque id=NAME,src=PATH -- buildkit reads the file, nothing is echoed.
+  args+=(--secret "${spec}")
+done
+if [ -n "${GIT_SHA:-}" ]; then
+  args+=(--opt "label:org.opencontainers.image.revision=${GIT_SHA}")
+fi
+if [ -n "${IMAGE_SOURCE:-}" ]; then
+  args+=(--opt "label:org.opencontainers.image.source=${IMAGE_SOURCE}")
+fi
+for kv in ${BUILD_ARGS:-}; do
+  args+=(--opt "build-arg:${kv}")
+done
+for kv in ${EXTRA_LABELS:-}; do
+  args+=(--opt "label:${kv}")
+done
+
+echo "build-image: building ${REF}"
+buildctl --addr "$BUILDKIT_HOST" build "${args[@]}" --output "type=oci,dest=${TAR_FILE}"
+
+# buildctl has no registry-push equivalent to `buildah push`, so skopeo copies
+# the OCI archive up -- once per tag, from the same archive, so every tag points
+# at bit-identical content.
+push_tag() {
+  echo "build-image: pushing ${1}"
+  skopeo copy --dest-tls-verify=false "oci-archive:${TAR_FILE}" "docker://${1}"
+}
+
+push_tag "$REF"
+if [ "$PUSH_LATEST" = "1" ]; then
+  push_tag "${REGISTRY}/${IMAGE}:latest"
+fi
+if [ -n "$VERSION_TAG" ]; then
+  push_tag "${REGISTRY}/${IMAGE}:${VERSION_TAG}"
+fi
+
+echo "✓ build-image: ${REF} pushed"

.gitea/workflows/cd.yml

@@ -58,53 +58,27 @@ jobs:
           REF="${{ github.ref }}"
           if [[ "$REF" == refs/tags/v* ]]; then
             echo "version-tag=${REF#refs/tags/}" >> "$GITHUB_OUTPUT"
+            echo "version=${REF#refs/tags/}" >> "$GITHUB_OUTPUT"
+          else
+            # The ldflags version stamp: git tag on a v* build, else short sha.
+            # Computed here in shell, not as a `${{ a || b }}` expression, so it
+            # cannot depend on how the runner treats an empty step output -- a
+            # wrong VERSION would be baked into the binary silently.
+            echo "version=${SHA}" >> "$GITHUB_OUTPUT"
           fi
 
       - name: Build and push to local registry
-        run: |
+      # infra#309: implementation lives in .gitea/build-image.sh, a
-          set -e
+      # byte-identical copy of mathias/infra's ci-templates/build-image.sh.
-          # infra#241: buildctl, not buildah. Rootless buildah in gitea-runner's
+      # Do not edit it here -- edit the canonical file, run `task ci:sync`,
-          # hardened securityContext (capabilities drop ALL,
+      # and infra's drift gate names any repo still carrying an old copy.
-          # allowPrivilegeEscalation false) cannot remap the UID/GID range
+        env:
-          # newuidmap/newgidmap need on a fresh base-image pull, and the pod has
+          SHA_TAG: ${{ steps.meta.outputs.sha-tag }}
-          # no OCI runtime at all -- so this Dockerfile's `RUN apk add` / `RUN go
+          VERSION_TAG: ${{ steps.meta.outputs.version-tag }}
-          # build` could not execute there either. buildctl is a thin client
+          GIT_SHA: ${{ github.sha }}
-          # that hands the build to the host's buildkitd over a socket, so the
+          IMAGE_SOURCE: ${{ github.repositoryUrl }}
-          # privileged layer work happens on the host and this pod's
+          BUILD_ARGS: VERSION=${{ steps.meta.outputs.version }}
-          # securityContext stops being in the picture. Same pattern as
+        run: bash .gitea/build-image.sh
-          # mathias/infra's segment-embedder.yml.
-          BUILDKIT_HOST="unix:///run/buildkit/buildkitd.sock"
-          REGISTRY="localhost:5000"
-          REF="${REGISTRY}/${{ env.IMAGE }}:${{ steps.meta.outputs.sha-tag }}"
-          # Stamp the real build version: the git tag on a v* build, else the short sha.
-          VERSION="${{ steps.meta.outputs.version-tag }}"
-          # `if`, not `[ -z ] &&`: under `set -e` the && form exits the step
-          # whenever VERSION is already set.
-          if [ -z "$VERSION" ]; then VERSION="${{ steps.meta.outputs.sha-tag }}"; fi
-          TAR_FILE="$(mktemp)"
-          trap 'rm -f "$TAR_FILE"' EXIT
-
-          buildctl --addr "$BUILDKIT_HOST" build \
-            --frontend dockerfile.v0 \
-            --local context=. \
-            --local dockerfile=. \
-            --opt build-arg:VERSION="${VERSION}" \
-            --opt label:org.opencontainers.image.revision="${{ github.sha }}" \
-            --opt label:org.opencontainers.image.source="${{ github.repositoryUrl }}" \
-            --output type=oci,dest="$TAR_FILE"
-
-          # buildctl has no registry-push equivalent to `buildah push`; skopeo
-          # copies the OCI archive up, once per tag.
-          skopeo copy --dest-tls-verify=false \
-            oci-archive:"$TAR_FILE" docker://${REF}
-          skopeo copy --dest-tls-verify=false \
-            oci-archive:"$TAR_FILE" docker://${REGISTRY}/${{ env.IMAGE }}:latest
-          if [ -n "${{ steps.meta.outputs.version-tag }}" ]; then
-            skopeo copy --dest-tls-verify=false \
-              oci-archive:"$TAR_FILE" \
-              docker://${REGISTRY}/${{ env.IMAGE }}:${{ steps.meta.outputs.version-tag }}
-          fi
-          echo "✓ Image pushed to ${REF}"
 
       # No smoke test here. The old one ran `sudo k3s ctr run` against the host's
       # containerd: written for the Arch host runner, impossible in the