feat(ci): retain recent release images

.gitea/workflows/container-cd.yml

@@ -45,6 +45,11 @@ on:
         required: false
         default: ""
         type: string
+      release_retention_count:
+        description: Number of immutable sha-* release images to retain after a successful promotion
+        required: false
+        default: 2
+        type: number
     secrets:
       REGISTRY_USERNAME:
         required: true
@@ -149,3 +154,90 @@ jobs:
           set -eu
           ssh -i ~/.ssh/id_ed25519 cicd-deploy@"${{ inputs.deploy_host }}" \
             "promote ${{ inputs.deploy_service }} ${{ inputs.image_name }}:sha-${{ gitea.sha }}"
+      - name: Retain current and previous release images
+        if: ${{ startsWith(gitea.ref, 'refs/tags/v') && inputs.deploy_service != '' && inputs.deploy_host != '' }}
+        env:
+          REGISTRY_USERNAME: ${{ secrets.REGISTRY_USERNAME }}
+          REGISTRY_PASSWORD: ${{ secrets.REGISTRY_PASSWORD }}
+        run: |
+          set -euo pipefail
+
+          image_name='${{ inputs.image_name }}'
+          keep_count='${{ inputs.release_retention_count }}'
+          current_version='sha-${{ gitea.sha }}'
+
+          case "$keep_count" in
+            ''|*[!0-9]*|0)
+              echo "release_retention_count must be a positive integer"
+              exit 1
+              ;;
+          esac
+
+          registry="${image_name%%/*}"
+          image_path="${image_name#*/}"
+          owner="${image_path%%/*}"
+          package_name="${image_path#*/}"
+
+          if [ "$registry" = "$image_name" ] || [ "$owner" = "$image_path" ]; then
+            echo "image_name must include registry, owner, and package name"
+            exit 1
+          fi
+          case "$owner/$package_name" in
+            *[!A-Za-z0-9._/-]*|*/*/*)
+              echo "image owner or package name contains unsupported characters"
+              exit 1
+              ;;
+          esac
+
+          api_base="https://${registry}/api/v1/packages"
+          versions_file="$(mktemp)"
+          keep_file="$(mktemp)"
+          trap 'rm -f "$versions_file" "$keep_file"' EXIT
+
+          page=1
+          while [ "$page" -le 100 ]; do
+            response="$(curl --fail --silent --show-error --retry 3 --retry-all-errors \
+              --user "$REGISTRY_USERNAME:$REGISTRY_PASSWORD" \
+              "${api_base}/${owner}?type=container&q=${package_name}&limit=50&page=${page}")"
+            item_count="$(printf '%s' "$response" | jq 'length')"
+            [ "$item_count" -gt 0 ] || break
+            printf '%s' "$response" | jq -r --arg package_name "$package_name" '
+              .[]
+              | select((.name | ascii_downcase) == ($package_name | ascii_downcase))
+              | select(.version | test("^sha-[0-9a-f]{40}$"))
+              | [.created_at, .version]
+              | @tsv
+            ' >> "$versions_file"
+            page=$((page + 1))
+          done
+
+          if ! awk -F '\t' -v current="$current_version" '$2 == current { found = 1 } END { exit(found ? 0 : 1) }' "$versions_file"; then
+            echo "Current release version was not returned by the Gitea Packages API: $current_version"
+            exit 1
+          fi
+
+          printf '%s\n' "$current_version" > "$keep_file"
+          previous_count=$((keep_count - 1))
+          if [ "$previous_count" -gt 0 ]; then
+            sort -r "$versions_file" | awk -F '\t' \
+              -v current="$current_version" \
+              -v limit="$previous_count" \
+              '$2 != current && kept < limit { print $2; kept++ }' >> "$keep_file"
+          fi
+
+          deleted=0
+          while IFS=$'\t' read -r _created_at version; do
+            [ -n "$version" ] || continue
+            if grep -Fqx "$version" "$keep_file"; then
+              echo "Keeping release image: $package_name:$version"
+              continue
+            fi
+            curl --fail --silent --show-error --retry 3 --retry-all-errors \
+              --user "$REGISTRY_USERNAME:$REGISTRY_PASSWORD" \
+              --request DELETE \
+              "${api_base}/${owner}/container/${package_name}/${version}"
+            echo "Deleted superseded release image: $package_name:$version"
+            deleted=$((deleted + 1))
+          done < <(sort -r "$versions_file")
+
+          echo "Release retention complete: package=$package_name retained=$keep_count deleted=$deleted"