Attach binaries to a release, for installs that are not containers

A release published an image and nothing else, so there was nothing for a
host install to download -- the only way to get the binary was to pull the
image and copy it out, which makes "install without Docker" depend on
Docker.

Each release now carries inbuxa-linux-amd64.tar.gz, inbuxa-linux-arm64.tar.gz
and SHA256SUMS, named as stalwart-migrator's are.

They are taken out of the image this pipeline just pushed rather than
compiled again. A second Rust build per architecture is the slowest thing
here, and it would leave two artifacts that are meant to be the same build
and only probably are. Extracting makes that identity a fact: the binary in
the tarball is the file the image runs. `docker create` starts nothing, so
copying a file out of an arm64 image on an amd64 runner needs no emulation.

One thing the extraction cannot carry: the image grants the binary
cap_net_bind_service, and a tar archive does not keep that xattr. The
release body says so, and says what to do instead -- setcap, or
AmbientCapabilities in the unit -- because a server that cannot bind 25 and
does not say why is a bad first hour.

Checked by hand against v2026.9.23 before this landed: both architectures
extract to the right ELF, and the amd64 binary runs on a bare Debian 13 with
every library resolved and reports its own version.

.gitea/workflows/publish.yml

@@ -131,8 +131,95 @@ jobs:
           except urllib.error.HTTPError as e:
               if e.code != 404: raise
           image = f"{os.environ['REGISTRY']}/{os.environ['REPO']}:{version}"
-          body = f"Container image: `{image}` (linux/amd64, linux/arm64); also `:latest`."
+          body = (f"Container image: `{image}` (linux/amd64, linux/arm64); also `:latest`.\n\n"
+                  "Binaries for a host install are attached: `inbuxa-linux-amd64.tar.gz` and "
+                  "`inbuxa-linux-arm64.tar.gz`, with `SHA256SUMS`. Each is the binary out of this "
+                  "release's image for that architecture, so it is the same build. The image "
+                  "grants it `cap_net_bind_service`; a host install has to grant that itself "
+                  "(`setcap`, or `AmbientCapabilities` in the unit) to bind port 25.")
           data = json.dumps({"tag_name": tag, "name": f"INBUXA {version}", "body": body}).encode()
           r = json.load(urllib.request.urlopen(urllib.request.Request(f"{api}/releases", data=data, headers=h)))
           print(f"created release {r['tag_name']}")
           PY
+
+  # The binaries for a host install, taken out of the image that was just
+  # pushed rather than compiled again.
+  #
+  # Building them separately would mean a second Rust build per architecture
+  # -- the slowest thing this pipeline does -- and would leave two artifacts
+  # that are supposed to be the same build but only probably are. Extracting
+  # them makes that identity a fact: the binary in the tarball is the file
+  # the image runs.
+  #
+  # `docker create` does not start anything, so pulling an arm64 image on an
+  # amd64 runner and copying a file out of it needs no emulation.
+  binaries:
+    needs: [version, publish, release]
+    runs-on: docker
+    container:
+      image: docker:28-cli@sha256:625d9431a9f54c5a2bc90f24f0e1c3d55b1349fd857dd85035f98c2c9acbdd4d # 28-cli
+      volumes:
+        - /var/run/docker.sock:/var/run/docker.sock
+    env:
+      REGISTRY: ${{ vars.REGISTRY }}
+      IMAGE: ${{ vars.REGISTRY }}/${{ github.repository }}
+      VERSION: ${{ needs.version.outputs.version }}
+      TAG: ${{ github.ref_name }}
+      REPO: ${{ github.repository }}
+      PACKAGE_TOKEN: ${{ secrets.PACKAGE_TOKEN }}
+      TOKEN: ${{ secrets.GITHUB_TOKEN }}
+    steps:
+      - name: take the binaries out of the image
+        run: |
+          set -euo pipefail
+          echo "$PACKAGE_TOKEN" | docker login -u jcoffey-dev --password-stdin "$REGISTRY"
+          mkdir -p /out && cd /out
+          for arch in amd64 arm64; do
+            docker pull -q --platform "linux/$arch" "$IMAGE:$VERSION"
+            id="$(docker create --platform "linux/$arch" "$IMAGE:$VERSION")"
+            docker cp "$id:/usr/local/bin/inbuxa" "inbuxa"
+            docker rm -f "$id" >/dev/null
+            chmod 0755 inbuxa
+            tar -czf "inbuxa-linux-$arch.tar.gz" inbuxa
+            rm inbuxa
+          done
+          sha256sum inbuxa-linux-*.tar.gz > SHA256SUMS
+          cat SHA256SUMS
+      - name: attach them to the release
+        run: |
+          set -euo pipefail
+          apk add --no-cache -q python3
+          python3 - <<'PY'
+          import json, os, urllib.request, urllib.error, uuid, pathlib
+          api = f"{os.environ['CI_SERVER_INTERNAL']}/api/v1/repos/{os.environ['REPO']}"
+          tok = {"Authorization": f"token {os.environ['TOKEN']}"}
+          tag = os.environ["TAG"]
+
+          def get(path):
+              return json.load(urllib.request.urlopen(urllib.request.Request(api + path, headers=tok)))
+
+          rel = get(f"/releases/tags/{tag}")
+          assets = {a["name"]: a["id"] for a in get(f"/releases/{rel['id']}/assets")}
+
+          for path in ["/out/inbuxa-linux-amd64.tar.gz", "/out/inbuxa-linux-arm64.tar.gz", "/out/SHA256SUMS"]:
+              name = os.path.basename(path)
+              # A re-run of a tag replaces its assets rather than leaving two
+              # files with the same name and different contents.
+              if name in assets:
+                  urllib.request.urlopen(urllib.request.Request(
+                      f"{api}/releases/{rel['id']}/assets/{assets[name]}", headers=tok, method="DELETE"))
+              boundary = uuid.uuid4().hex
+              body = b"".join([
+                  f"--{boundary}\r\nContent-Disposition: form-data; name=\"attachment\"; filename=\"{name}\"\r\n".encode(),
+                  b"Content-Type: application/octet-stream\r\n\r\n",
+                  pathlib.Path(path).read_bytes(),
+                  f"\r\n--{boundary}--\r\n".encode(),
+              ])
+              req = urllib.request.Request(
+                  f"{api}/releases/{rel['id']}/assets?name={name}", data=body, method="POST",
+                  headers={**tok, "Content-Type": f"multipart/form-data; boundary={boundary}"})
+              urllib.request.urlopen(req)
+              print("attached", name)
+          PY
+      - if: always()
+        run: docker logout "$REGISTRY" || true