ci: add a workflow that lints commit messages

.github/workflows/lint.yml

@@ -0,0 +1,22 @@
+name: lint
+
+on:
+  push:
+    branches:
+      - master
+      - ci
+      - 'release/**'
+  pull_request:
+    branches: [master]
+
+jobs:
+  commit-msg:
+    runs-on: ubuntu-latest
+    steps:
+      - uses: actions/checkout@v3
+        with:
+          fetch-depth: 50
+
+      - name: Lint
+        run: |
+          ./ci/lint-commit-msg.py

ci/lint-commit-msg.py

@@ -0,0 +1,112 @@
+#!/usr/bin/env python3
+import os, sys, json, subprocess, re
+
+def call(cmd) -> str:
+	sys.stdout.flush()
+	ret = subprocess.run(cmd, check=True, stdout=subprocess.PIPE, text=True)
+	return ret.stdout
+
+lint_rules = {}
+
+def lint_rule(description: str):
+	def f(func):
+		assert func.__name__ not in lint_rules.keys()
+		lint_rules[func.__name__] = (func, description)
+	return f
+
+def get_commit_range() -> str:
+	if len(sys.argv) > 1:
+		return sys.argv[1]
+	# https://github.com/actions/runner/issues/342#issuecomment-590670059
+	event_name = os.environ["GITHUB_EVENT_NAME"]
+	with open(os.environ["GITHUB_EVENT_PATH"], "rb") as f:
+		event = json.load(f)
+	if event_name == "push":
+		if event["created"] or event["forced"]:
+			print("Skipping logic on branch creation or force-push")
+			return None
+		return event["before"] + "..." + event["after"]
+	elif event_name == "pull_request":
+		return event["pull_request"]["base"]["sha"] + ".." + event["pull_request"]["head"]["sha"]
+
+def do_lint(commit_range: str) -> bool:
+	commits = call(["git", "log", "--pretty=format:%h %s", commit_range]).splitlines()
+	print(f"Linting {len(commits)} commit(s):")
+	any_failed = False
+	for commit in commits:
+		sha, _, _ = commit.partition(' ')
+		#print(commit)
+		body = call(["git", "show", "-s", "--format=%B", sha]).splitlines()
+		failed = []
+		if len(body) == 0:
+			failed.append("* Commit message must not be empty")
+		else:
+			for k, v in lint_rules.items():
+				if not v[0](body):
+					failed.append(f"* {v[1]} [{k}]")
+		if failed:
+			any_failed = True
+			print("-" * 40)
+			sys.stdout.flush()
+			subprocess.run(["git", "-P", "show", "-s", sha])
+			print("\nhas the following issues:")
+			print("\n".join(failed))
+			print("-" * 40)
+	return any_failed
+
+################################################################################
+
+NO_PREFIX_WHITELIST = r"^Revert \"(.*)\"|^Release [0-9]|^Update VERSION$"
+
+@lint_rule("Subject line must contain a prefix identifying the sub system")
+def subsystem_prefix(body):
+	if re.search(NO_PREFIX_WHITELIST, body[0]):
+		return True
+	m = re.search(r"^([^:]+):\s", body[0])
+	if not m:
+		return False
+	# a comma-separated list is okay
+	s = re.sub(r",\s+", "", m.group(1))
+	# but no spaces otherwise
+	return not " " in s
+
+@lint_rule("First word after : must be lower case")
+def description_lowercase(body):
+	if re.search(NO_PREFIX_WHITELIST, body[0]):
+		return True
+	return re.search(r":\s+[a-z0-9]", body[0])
+
+@lint_rule("Subject line must not end with a full stop")
+def no_dot(body):
+	return not body[0].rstrip().endswith('.')
+
+@lint_rule("There must be an empty line between subject and extended description")
+def empty_line(body):
+	return len(body) == 1 or body[1].strip() == ""
+
+# been seeing this one all over github lately, must be the webshits
+@lint_rule("Do not use 'conventional commits' style")
+def no_cc(body):
+	return not re.search(r"(?i)^(feat|fix|chore|refactor)[!:(]", body[0])
+
+@lint_rule("History must be linear, no merge commits")
+def no_merge(body):
+	return not body[0].startswith("Merge ")
+
+@lint_rule("Subject line should be shorter than 72 characters")
+def line_too_long(body):
+	return len(body[0]) <= 72
+
+@lint_rule("Prefix should not include C file extensions (use `vo_gpu: ...` not `vo_gpu.c: ...`)")
+def no_file_exts(body):
+	return not re.search(r"[a-z0-9]\.[ch]:\s", body[0])
+
+################################################################################
+
+if __name__ == "__main__":
+	commit_range = get_commit_range()
+	if commit_range is None:
+		exit(0)
+	print("Commit range:", commit_range)
+	any_failed = do_lint(commit_range)
+	exit(1 if any_failed else 0)