ci: prune old releases to keep only latest per branch

After uploading new release assets, delete older beta releases (dev)
or older stable releases (main) to conserve disk. Only the latest
build per branch is kept on the Forgejo instance; older builds are
available on mirrored free hosting.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

.forgejo/workflows/build.yml

@@ -114,3 +114,36 @@ jobs:
             fi
             echo "Uploaded ${FILENAME} (HTTP ${HTTP_CODE})"
           done
+
+      - name: Prune old releases
+        run: |
+          TAG_PREFIX="${{ github.ref_name == 'main' && 'v6' || 'v6.*-beta' }}"
+          CURRENT_ID="${{ steps.create_release.outputs.id }}"
+          echo "Keeping release ${CURRENT_ID}, pruning older ${TAG_PREFIX} releases..."
+          PAGE=1
+          while true; do
+            RELEASES=$(curl -s "${FORGEJO_URL}/api/v1/repos/${{ github.repository }}/releases?limit=50&page=${PAGE}" \
+              -H "Authorization: token ${{ secrets.RELEASE_TOKEN }}")
+            COUNT=$(echo "$RELEASES" | python3 -c "import sys,json; print(len(json.load(sys.stdin)))" 2>/dev/null || echo 0)
+            [ "$COUNT" = "0" ] && break
+            echo "$RELEASES" | python3 -c "
+          import sys, json, fnmatch
+          for r in json.load(sys.stdin):
+              rid = r['id']
+              tag = r['tag_name']
+              if rid == ${CURRENT_ID}:
+                  continue
+              if fnmatch.fnmatch(tag, '${TAG_PREFIX}*'):
+                  print(f'{rid} {tag}')
+          " | while read -r RID RTAG; do
+              echo "Deleting release ${RTAG} (id=${RID})"
+              curl -s -o /dev/null -X DELETE \
+                "${FORGEJO_URL}/api/v1/repos/${{ github.repository }}/releases/${RID}" \
+                -H "Authorization: token ${{ secrets.RELEASE_TOKEN }}"
+              curl -s -o /dev/null -X DELETE \
+                "${FORGEJO_URL}/api/v1/repos/${{ github.repository }}/tags/${RTAG}" \
+                -H "Authorization: token ${{ secrets.RELEASE_TOKEN }}"
+            done
+            PAGE=$((PAGE + 1))
+          done
+          echo "Prune complete"