forgejo/lint_commit_msg: add script for commit message linting

Based on mpv's script, under LGPL. https://github.com/mpv-player/mpv

Co-authored-by: Timo Rothenpieler <timo@rothenpieler.org>
Signed-off-by: Kacper Michajłow <kasper93@gmail.com>

.forgejo/pre-commit/lint_commit_msg.py

@@ -0,0 +1,138 @@
+#!/usr/bin/env python3
+import json
+import os
+import re
+import subprocess
+import sys
+import urllib.request as request
+from collections.abc import Callable
+
+LintBody = list[str]
+LintFunction = Callable[[LintBody], bool]
+LintRule = tuple[LintFunction, str]
+
+def call(cmd: list[str]) -> str:
+    sys.stdout.flush()
+    ret = subprocess.run(cmd, check=True, stdout=subprocess.PIPE, encoding="utf-8", text=True)
+    return ret.stdout
+
+lint_rules: dict[str, LintRule] = {}
+
+# A lint rule should return True if everything is okay
+def lint_rule(description: str) -> Callable[[LintFunction], None]:
+    def f(func: LintFunction) -> None:
+        assert func.__name__ not in lint_rules
+        lint_rules[func.__name__] = (func, description)
+    return f
+
+def get_pr_commits() -> list[tuple[str, list[str]]]:
+    pr_number = os.environ["GITHUB_REF"].split("/")[2]
+    api_url = os.environ["GITHUB_API_URL"]
+    repo = os.environ["GITHUB_REPOSITORY"]
+
+    url = f"{api_url}/repos/{repo}/pulls/{pr_number}/commits"
+    req = request.Request(url)
+    req.add_header("Accept", "application/vnd.github+json")
+    if "GITHUB_TOKEN" in os.environ:
+        req.add_header("Authorization", f"token {os.environ['GITHUB_TOKEN']}")
+
+    with request.urlopen(req) as response:
+        commits = json.load(response)
+
+    res = []
+    for commit in commits:
+        sha = commit["sha"]
+        message = commit["commit"]["message"]
+        res.append((sha, message.splitlines()))
+
+    return res
+
+def get_commits() -> list[tuple[str, list[str]]]:
+    if os.environ.get("GITHUB_EVENT_NAME") == "pull_request":
+        return get_pr_commits()
+
+    commit_range = sys.argv[1] if len(sys.argv) > 1 else None
+    if not commit_range:
+        return []
+
+    commits = call(["git", "log", "-z", "--pretty=format:%H%n%B", commit_range]).split("\x00")
+    res = []
+    for commit in commits:
+        if not commit.strip():
+            continue
+        sha, message = commit.split("\n", 1)
+        res.append((sha, message.splitlines()))
+
+    return res
+
+def lint_commit_message(body: list[str]) -> list[str]:
+    failed = []
+    assert len(body) > 0, "Commit message must not be empty"
+    for k, v in lint_rules.items():
+        if not v[0](body):
+            failed.append(f"* {v[1]} [{k}]")
+
+    return failed
+
+def lint(commits: list[tuple[str, list[str]]]) -> bool:
+    print(f"Linting {len(commits)} commit(s):")
+    any_failed = False
+    for sha, body in commits:
+        if failed := lint_commit_message(body):
+            any_failed = True
+            print("-" * 40)
+            if os.environ.get("GITHUB_EVENT_NAME") == "pull_request":
+                print(f"Commit {sha[:8]}: {body[0] if body else "(empty)"}")
+            else:
+                sys.stdout.flush()
+                subprocess.run(["git", "-P", "show", "-s", sha])
+            print("\nhas the following issues:")
+            print("\n".join(failed))
+            print("-" * 40)
+
+    return not any_failed
+
+
+NO_PREFIX_WHITELIST = \
+    r"^Revert \"(.*)\"|^Reapply \"(.*)\""
+
+@lint_rule("Subject line must contain a prefix identifying the sub system")
+def subsystem_prefix(body: LintBody) -> bool:
+    return bool(re.search(NO_PREFIX_WHITELIST, body[0]) or
+                re.search(r"^[\w/\.{},-]+: ", body[0]))
+
+@lint_rule("First word after : must be lower case")
+def description_lowercase(body: LintBody) -> bool:
+    # Allow all caps for acronyms and options with --
+    return bool(re.search(NO_PREFIX_WHITELIST, body[0]) or
+                re.search(r": (?:[A-Z]{2,} |--[a-z]|[a-z0-9])", body[0]))
+
+@lint_rule("Subject line must not end with a full stop")
+def no_dot(body: LintBody) -> bool:
+    return not body[0].rstrip().endswith(".")
+
+@lint_rule("There must be an empty line between subject and extended description")
+def empty_line(body: LintBody) -> bool:
+    return len(body) == 1 or body[1].strip() == ""
+
+@lint_rule("Do not use 'conventional commits' style")
+def no_cc(body: LintBody) -> bool:
+    return not re.search(r"(?i)^(feat|fix|chore|refactor)[!:(]", body[0])
+
+@lint_rule("Subject line should be shorter than 120 characters")
+def line_too_long(body: LintBody) -> bool:
+    revert = re.search(r"^Revert \"(.*)\"|^Reapply \"(.*)\"", body[0])
+    return bool(revert or len(body[0]) <= 120)
+
+@lint_rule("Prefix should not include file extension")
+def no_file_exts(body: LintBody) -> bool:
+    return not re.search(r"[a-z0-9]\.([chm]|texi): ", body[0])
+
+
+if __name__ == "__main__":
+    commits = get_commits()
+    if not commits:
+        print("Usage: ./lint_commits.py <commit-range>")
+        exit(1)
+    if not lint(commits):
+        exit(2)

.forgejo/workflows/lint.yml

@@ -5,6 +5,17 @@ on:
   pull_request:
 
 jobs:
+  commit_msg:
+    runs-on: utilities
+    if: ${{ forge.event_name == 'pull_request' }}
+    steps:
+      - name: Checkout
+        uses: actions/checkout@v4
+        with:
+          sparse-checkout: .forgejo/pre-commit
+      - name: Lint
+        run: .forgejo/pre-commit/lint_commit_msg.py
+
   lint:
     runs-on: utilities
     steps: