Support rebuilding historical versions via IMPLEMENTATION_VERSION

Pin the installed jschon version from an optional build arg so build-all can
(re)build and publish images for past versions, giving the UI a per-version
compliance trend. An empty value (the normal build) installs the latest.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

Author: Julian

.github/workflows/build-all.yml

@@ -26,12 +26,16 @@ jobs:
       - name: Collect available versions
         id: revisions
         run: |
-          # Only the auto-created per-version release tags, plus current `main`.
-          tags=$(jq -c -n '$ARGS.positional + ["main"]' --args $(git tag --list 'harness-release-*'))
-          echo "value=${tags}" >> "$GITHUB_OUTPUT"
+          # Each historical version is a {ref, version} pair: the tag to check out and the
+          # version to pin via the `IMPLEMENTATION_VERSION` build arg.
+          # `main` builds the current default (unpinned) and is additionally tagged `latest`.
+          revisions=$(git tag --list 'harness-release-*' \
+            | jq -R -c '{ref: ., version: ltrimstr("harness-release-")}' \
+            | jq -s -c '. + [{ref: "main", version: ""}]')
+          echo "value=${revisions}" >> "$GITHUB_OUTPUT"
 
   build:
-    name: Build
+    name: Build (${{ matrix.revision.ref }})
     needs: versions
     strategy:
       # Backfill as many versions as possible; don't abort the rest on one failure.
@@ -46,6 +50,7 @@ jobs:
       artifact-metadata: write # needed for build provenance attestation
     uses: bowtie-json-schema/bowtie/.github/workflows/harness-ci.yml@a0ae283dca0a0d0eb2381a886d5499162f33c82a # main
     with:
-      ref: ${{ matrix.revision }}
+      ref: ${{ matrix.revision.ref }}
+      build-args: ${{ matrix.revision.version != '' && format('IMPLEMENTATION_VERSION={0}', matrix.revision.version) || '' }}
       publish: true
-      is-latest: ${{ matrix.revision == 'main' }}
+      is-latest: ${{ matrix.revision.ref == 'main' }}

Dockerfile

@@ -1,5 +1,8 @@
 FROM python:3.15.0b4-alpine
 WORKDIR /usr/src/myapp
-RUN python3 -m pip install jschon
+# Optionally pin the installed version so `build-all` can rebuild historical versions.
+# An empty value (the normal build) installs the latest release.
+ARG IMPLEMENTATION_VERSION
+RUN python3 -m pip install "jschon${IMPLEMENTATION_VERSION:+==${IMPLEMENTATION_VERSION}}"
 COPY bowtie_jschon.py .
 CMD ["python3", "bowtie_jschon.py"]