build: add author's GitHub id to changelog file

OPA uses the changelog file to recognize people who contribute to the
project by mentioning them in it. This commit introduces a way to fetch
the GitHub handle for the commit authors if they are not listed in the
MAINTAINERS.md file. It makes use of the GitHub API to do so, and thus
introduces an optional cli argument to pass the token to authenticate
requests, without which you might run into rate limit errors if you run
the script a couple of times.

Fixes #2323
Signed-off-by: Aditya <aditya10699@gmail.com>

build/changelog.py

@@ -7,10 +7,13 @@
 import subprocess
 import shlex
 import re
+import urllib2
+import sys
+import json
 
 
 def run(cmd, *args, **kwargs):
-    return subprocess.check_output(shlex.split(cmd), *args, **kwargs)
+    return subprocess.check_output(shlex.split(cmd), *args, **kwargs).decode('utf-8')
 
 
 def get_commit_ids(from_commit, to_commit):
@@ -26,6 +29,67 @@ def get_commit_message(commit_id):
     return run(cmd)
 
 
+def fetch(url, token):
+    req = urllib2.Request(url)
+    if token:
+        req.add_header('Authorization', "token {}".format(token))
+    try:
+        rsp = urllib2.urlopen(req)
+        result = json.loads(rsp.read())
+    except Exception as e:
+        if hasattr(e, 'reason'):
+            print >> sys.stderr, 'Failed to fetch URL {}: {}'.format(url, e.reason)
+        elif hasattr(e, 'code'):
+            print >> sys.stderr, 'Failed to fetch URL {}: Code {}'.format(url, e.code)
+        return {}
+    else:
+        return result
+
+
+def get_maintainers():
+    with open("MAINTAINERS.md", "r") as f:
+        contents = f.read()
+    maintainers = re.findall(r"[^\s]+@[^\s]+", contents)
+    return maintainers
+
+maintainers = get_maintainers()
+
+
+def is_maintainer(commit_message):
+    author = author_email(commit_message)
+    return author in maintainers
+
+
+def author_email(commit_message):
+    match = re.search(r"<(.*@.*)>", commit_message)
+    author = match.group(1)
+    return str(author)
+
+
+github_ids = {}
+def get_github_id(commit_message, commit_id, token):
+    email = author_email(commit_message)
+    if github_ids.get(email, ""):
+        return github_ids[email]
+    url = "https://api.github.com/repos/open-policy-agent/opa/commits/{}".format(commit_id)
+    r = fetch(url, token)
+    author = r.get('author', {})
+    if author is None:
+        return ""
+    login = author.get('login', '')
+    if login:
+        github_ids[email]=login
+        return login
+    return ""
+
+
+def mention_author(commit_message, commit_id, token):
+    username = get_github_id(commit_message, commit_id, token)
+    if username:
+        return "authored by @[{author}](https://github.com/{author})".format(author=username)
+    return ""
+
+
 def fixes_issue_id(commit_message):
     match = re.search(r"Fixes:?\s*#(\d+)", commit_message)
     if match:
@@ -36,11 +100,11 @@ def get_subject(commit_message):
     return commit_message.splitlines()[0]
 
 
-def get_changelog_message(commit_message, repo_url):
+def get_changelog_message(commit_message, mention, repo_url):
     issue_id = fixes_issue_id(commit_message)
     if issue_id:
         subject = get_subject(commit_message)
-        return "Fixes", "{subject} ([#{issue_id}]({repo_url}/issues/{issue_id}))".format(subject=subject, issue_id=issue_id, repo_url=repo_url)
+        return "Fixes", "{subject} ([#{issue_id}]({repo_url}/issues/{issue_id})) {mention}".format(subject=subject, issue_id=issue_id, repo_url=repo_url, mention=mention)
     return None, get_subject(commit_message)
 
 
@@ -53,6 +117,7 @@ def parse_args():
     parser = argparse.ArgumentParser()
     parser.add_argument(
         "--repo_url", default="https://github.com/open-policy-agent/opa")
+    parser.add_argument("--token", default="", help="GitHub API token")
     parser.add_argument("from_version", nargs="?",
                         default=get_latest_tag(), help="start of changes")
     parser.add_argument("to_commit", nargs="?",
@@ -64,10 +129,12 @@ def main():
 
     args = parse_args()
     changelog = {}
-
     for commit_id in get_commit_ids(args.from_version, args.to_commit):
+        mention = ""
         commit_message = get_commit_message(commit_id)
-        group, line = get_changelog_message(commit_message, args.repo_url)
+        if not is_maintainer(commit_message):
+            mention = mention_author(commit_message, commit_id, args.token)
+        group, line = get_changelog_message(commit_message, mention, args.repo_url)
         changelog.setdefault(group, []).append(line)
 
     if "Fixes" in changelog: