ci: auto-bump Homebrew tap on stable release tags (#938) (#976)

After the GitHub Release is published, push an updated Cask to
binaricat/homebrew-netcatty so `brew install binaricat/netcatty/netcatty`
stays current within minutes of the release. Stable tags only — prerelease
tags (v1.2.0-rc.1 etc.) are skipped to keep brew users on stable.

Implementation:
- New script .github/scripts/bump-homebrew-cask.sh computes SHA-256 of the
  arm64 + x64 DMGs already downloaded by the release job, sed-patches the
  Cask file in the tap repo, sanity-checks the result parses as Ruby, and
  pushes the bump. Idempotent on re-run when checksums match.
- New homebrew-tap job in build.yml runs after the release job on the same
  stable-tag gate, downloads the macOS artifact bundle, then runs the
  bump script with HOMEBREW_TAP_TOKEN.

Requires HOMEBREW_TAP_TOKEN secret with contents:write on
binaricat/homebrew-netcatty. With the secret missing the job will fail
fast at the env-var check with no side effects (no push attempted).

Co-authored-by: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

.github/scripts/bump-homebrew-cask.sh

@@ -0,0 +1,89 @@
+#!/usr/bin/env bash
+#
+# bump-homebrew-cask.sh — push a new version of the Netcatty cask to the
+# binaricat/homebrew-netcatty tap.
+#
+# Called from the release pipeline (`build.yml` → `homebrew-tap` job) after
+# the GitHub Release has been published with the signed + notarized DMGs.
+# Computes SHA-256 of the arm64 and x64 DMGs, rewrites the cask file, and
+# pushes the bump back to the tap repository using HOMEBREW_TAP_TOKEN.
+#
+# Required env vars:
+#   VERSION              — semver without leading "v" (e.g. 1.1.6)
+#   HOMEBREW_TAP_TOKEN   — PAT with contents:write on the tap repo
+#
+# Optional env vars:
+#   TAP_REPO             — default: binaricat/homebrew-netcatty
+#   ARTIFACTS_DIR        — default: artifacts
+#   CASK_PATH            — default: Casks/netcatty.rb
+set -euo pipefail
+
+: "${VERSION:?VERSION env var required (no leading v)}"
+: "${HOMEBREW_TAP_TOKEN:?HOMEBREW_TAP_TOKEN env var required}"
+
+TAP_REPO="${TAP_REPO:-binaricat/homebrew-netcatty}"
+ARTIFACTS_DIR="${ARTIFACTS_DIR:-artifacts}"
+CASK_PATH="${CASK_PATH:-Casks/netcatty.rb}"
+
+ARM_DMG="${ARTIFACTS_DIR}/Netcatty-${VERSION}-mac-arm64.dmg"
+X64_DMG="${ARTIFACTS_DIR}/Netcatty-${VERSION}-mac-x64.dmg"
+
+for f in "$ARM_DMG" "$X64_DMG"; do
+  if [[ ! -f "$f" ]]; then
+    echo "::error::Required DMG artifact not found: $f"
+    exit 1
+  fi
+done
+
+ARM_SHA=$(shasum -a 256 "$ARM_DMG" | awk '{print $1}')
+X64_SHA=$(shasum -a 256 "$X64_DMG" | awk '{print $1}')
+
+echo "Computed checksums:"
+echo "  arm64: ${ARM_SHA}"
+echo "  x64  : ${X64_SHA}"
+
+TMP=$(mktemp -d)
+trap 'rm -rf "$TMP"' EXIT
+
+git clone --depth 1 \
+  "https://x-access-token:${HOMEBREW_TAP_TOKEN}@github.com/${TAP_REPO}.git" \
+  "$TMP/tap"
+cd "$TMP/tap"
+
+if [[ ! -f "$CASK_PATH" ]]; then
+  echo "::error::Cask file not found in tap: $CASK_PATH"
+  exit 1
+fi
+
+# Patch the cask in place. The three lines we touch are anchored well enough
+# that we don't need anything fancier than sed:
+#   - the `version "X.Y.Z"` line (single line, anchored to start)
+#   - the `sha256 arm:   "..."` line
+#   - the `       intel: "..."` line (anchor on "intel:" at start, after the
+#     leading whitespace, so we don't accidentally match the `arch arm:
+#     "...", intel: "..."` line earlier in the file)
+sed -i -E 's|^(\s*version)\s+"[^"]+"|\1 "'"$VERSION"'"|' "$CASK_PATH"
+sed -i -E 's|(sha256\s+arm:\s+)"[^"]+"|\1"'"$ARM_SHA"'"|' "$CASK_PATH"
+sed -i -E 's|^(\s*intel:\s+)"[^"]+"|\1"'"$X64_SHA"'"|' "$CASK_PATH"
+
+# Sanity-check: parsed file should still be valid Ruby. Catches a broken
+# substitution before we push.
+if command -v ruby >/dev/null 2>&1; then
+  ruby -c "$CASK_PATH" >/dev/null
+fi
+
+if git diff --quiet; then
+  echo "Cask already at ${VERSION} with matching checksums — nothing to push."
+  exit 0
+fi
+
+echo "Cask diff:"
+git --no-pager diff "$CASK_PATH"
+
+git config user.email "github-actions[bot]@users.noreply.github.com"
+git config user.name "github-actions[bot]"
+git add "$CASK_PATH"
+git commit -m "Bump netcatty to ${VERSION}"
+git push origin HEAD:main
+
+echo "Pushed bump for ${VERSION} to ${TAP_REPO}."

.github/workflows/build.yml

@@ -604,3 +604,33 @@ jobs:
           generate_release_notes: true
           fail_on_unmatched_files: false
           token: ${{ secrets.RELEASE_TOKEN }}
+
+  homebrew-tap:
+    name: bump homebrew tap
+    runs-on: ubuntu-latest
+    needs: release
+    # Only stable release tags update the Cask. Prerelease tags
+    # (e.g. v1.2.0-rc.1) are skipped so brew users stay on stable.
+    if: |
+      startsWith(github.ref, 'refs/tags/v')
+      && !contains(github.ref_name, '-')
+      && (github.event_name == 'push' || (github.event_name == 'workflow_dispatch' && inputs.publish_release))
+    steps:
+      - name: Checkout
+        uses: actions/checkout@v4
+
+      - name: Download macOS artifacts
+        uses: actions/download-artifact@v4
+        with:
+          name: netcatty-macos
+          path: artifacts/
+
+      - name: Bump Cask in binaricat/homebrew-netcatty
+        env:
+          HOMEBREW_TAP_TOKEN: ${{ secrets.HOMEBREW_TAP_TOKEN }}
+          ARTIFACTS_DIR: artifacts
+        run: |
+          # Strip the leading "v" — Cask version is plain semver.
+          VERSION="${GITHUB_REF_NAME#v}"
+          export VERSION
+          bash .github/scripts/bump-homebrew-cask.sh