ci: enforce commit message conventions

Cherry-pick pull request redpwn#522 from redpwn/ci/commit-check

Author: ethanwu10

.github/workflows/ci.yml

@@ -5,14 +5,27 @@ on:
   pull_request:
 
 jobs:
+  check-commits:
+    runs-on: ubuntu-latest
+    if: github.event_name == 'pull_request'
+    steps:
+    - uses: actions/checkout@v2
+      with:
+        # Fetch all history
+        fetch-depth: 0
+
+    - name: Check commit messages
+      run: |
+        scripts/check-commits.sh ${{ github.event.pull_request.base.sha }} ${{ github.event.pull_request.head.sha }}
+
   shellcheck:
     runs-on: ubuntu-latest
     steps:
     - uses: actions/checkout@v2
 
     - name: Shellcheck
       run: |
-        shellcheck install/*.sh
+        shellcheck install/*.sh scripts/*.sh
 
   lint:
     runs-on: ubuntu-latest

CONTRIBUTING.md

@@ -52,7 +52,6 @@ You should follow the examples below as a guideline for how to name your branche
 ```
 feature/brief-description-here
 fix/bug-description
-style/some-frontend-component
 refactor/some-component
-add/contributing-md
+docs/some-component
 ```

scripts/check-commits.sh

@@ -0,0 +1,32 @@
+#!/bin/bash
+
+set -eo pipefail
+
+do_check() {
+	set -eo pipefail
+
+	base="$1"
+	head="$2"
+	log="$(git log --pretty='format:%h %s' --no-merges "${base}..${head}")"
+	if [ -z "$log" ]; then
+		echo 'WARNING: no commits in specified range' >&2
+	fi
+	grep -vE '^[0-9a-f]+ (feat|fix|refactor|docs|chore|build|test|ci|style)(\([a-zA-Z-]+\))?:' <<<"$log" || true
+}
+
+if [ $# -ne 2 ]; then
+	cat >&2 <<EOF
+Usage:
+    $0 BASE HEAD
+EOF
+	exit 1
+fi
+
+output="$(do_check "$1" "$2")"
+if [ -n "$output" ]; then
+	echo 'Bad commit messages:'
+	echo "$output"
+	exit 1
+else
+	echo 'All commit messages OK'
+fi