chore(ci): restrict commit types to chore, feat and fix

.github/conventional-subject.sh

@@ -0,0 +1,15 @@
+#!/usr/bin/env bash
+set -euo pipefail
+
+status=0
+
+while IFS= read -r subject; do
+  [ -n "$subject" ] || continue
+
+  if ! printf '%s' "$subject" | grep -qE '^(chore|feat|fix)(\([a-z0-9._-]+\))?!?: .+'; then
+    echo "::error::\"$subject\" must start with chore:, feat: or fix:, optionally scoped. Squash merging takes the pull request title as the commit subject, and release-please only recognises those three types."
+    status=1
+  fi
+done
+
+exit $status

.github/release-please-config.json

@@ -15,7 +15,7 @@
     {
       "type": "chore",
       "section": "Miscellaneous",
-      "hidden": true
+      "hidden": false
     }
   ],
   "plugins": [

.github/workflows/main-subjects.yml

@@ -0,0 +1,31 @@
+name: Main subjects
+
+on:
+  push:
+    branches:
+      - main
+
+permissions:
+  contents: read
+
+jobs:
+  conventional:
+    name: Landed commit types
+    runs-on: ubuntu-latest
+    steps:
+    - uses: actions/checkout@a37ce9120846195fa4ece8f58b268e6043cb2f26 # v3.7.0
+      with:
+        fetch-depth: 0
+
+    - name: Check the landed subjects
+      env:
+        BEFORE: ${{ github.event.before }}
+        AFTER: ${{ github.sha }}
+      run: |
+        if git cat-file -e "$BEFORE^{commit}" 2>/dev/null; then
+          revisions=("$BEFORE..$AFTER")
+        else
+          revisions=(--max-count=1 "$AFTER")
+        fi
+
+        git log --no-merges --format=%s "${revisions[@]}" | .github/conventional-subject.sh

.github/workflows/pr-title.yml

@@ -0,0 +1,24 @@
+name: PR title
+
+on:
+  pull_request:
+    types:
+      - opened
+      - edited
+      - reopened
+      - synchronize
+
+permissions:
+  contents: read
+
+jobs:
+  conventional:
+    name: Conventional commit type
+    runs-on: ubuntu-latest
+    steps:
+    - uses: actions/checkout@a37ce9120846195fa4ece8f58b268e6043cb2f26 # v3.7.0
+
+    - name: Check the title
+      env:
+        TITLE: ${{ github.event.pull_request.title }}
+      run: printf '%s\n' "$TITLE" | .github/conventional-subject.sh