Add script 'release/update-manpages' to generate manpages

Debian package started to ship manpages for repo since 2.8 [1]
And it's about for one year. So I think it should be upstreamed.

The script depends on help2man, which is available in both debian [2]
and ubuntu [3].

[1] https://tracker.debian.org/news/1150858/accepted-repo-28-1-source-into-unstable
[2] https://tracker.debian.org/pkg/help2man
[3] https://launchpad.net/ubuntu/+source/help2man

Change-Id: Ide2b356d0944ebde34cc96c6d5a782655bd72288
Signed-off-by: Roger Shimizu <rosh@debian.org>
Reviewed-on: https://gerrit-review.googlesource.com/c/git-repo/+/309782
Reviewed-by: Mike Frysinger <vapier@google.com>

release/update-manpages

@@ -0,0 +1,85 @@
+#!/usr/bin/env python3
+# Copyright (C) 2021 The Android Open Source Project
+#
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+#
+#      http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+
+"""Helper tool for generating manual page for all repo commands.
+
+This is intended to be run before every official Repo release.
+"""
+
+from pathlib import Path
+from functools import partial
+import argparse
+import multiprocessing
+import os
+import re
+import shutil
+import subprocess
+import sys
+import tempfile
+
+TOPDIR = Path(__file__).resolve().parent.parent
+MANDIR = TOPDIR.joinpath('man')
+
+# Load repo local modules.
+sys.path.insert(0, str(TOPDIR))
+from git_command import RepoSourceVersion
+import subcmds
+
+def worker(cmd, **kwargs):
+  subprocess.run(cmd, **kwargs)
+
+def main(argv):
+  parser = argparse.ArgumentParser(description=__doc__)
+  opts = parser.parse_args(argv)
+
+  if not shutil.which('help2man'):
+    sys.exit('Please install help2man to continue.')
+
+  # "repo branch" is an alias for "repo branches".
+  del subcmds.all_commands['branch']
+  (MANDIR / 'repo-branch.1').write_text('.so man1/repo-branches.1')
+
+  version = RepoSourceVersion()
+  cmdlist = [['help2man', '-N', '-n', f'repo {cmd} - manual page for repo {cmd}',
+    '-S', f'repo {cmd}', '-m', 'Repo Manual', f'--version-string={version}',
+    '-o', MANDIR.joinpath(f'repo-{cmd}.1'), TOPDIR.joinpath('repo'),
+    '-h', f'help {cmd}'] for cmd in subcmds.all_commands]
+  cmdlist.append(['help2man', '-N', '-n', 'repository management tool built on top of git',
+    '-S', 'repo', '-m', 'Repo Manual', f'--version-string={version}',
+    '-o', MANDIR.joinpath('repo.1'), TOPDIR.joinpath('repo'),
+    '-h', 'help --all'])
+
+  with tempfile.TemporaryDirectory() as tempdir:
+    repo_dir = Path(tempdir) / '.repo'
+    repo_dir.mkdir()
+    (repo_dir / 'repo').symlink_to(TOPDIR)
+
+    # Run all cmd in parallel, and wait for them to finish.
+    with multiprocessing.Pool() as pool:
+      pool.map(partial(worker, cwd=tempdir, check=True), cmdlist)
+
+  regex = (
+      (r'(It was generated by help2man) [0-9.]+', '\g<1>.'),
+      (r'^\.IP\n(.*:)\n', '.SS \g<1>\n'),
+      (r'^\.PP\nDescription', '.SH DETAILS'),
+  )
+  for path in MANDIR.glob('*.1'):
+    data = path.read_text()
+    for pattern, replacement in regex:
+      data = re.sub(pattern, replacement, data, flags=re.M)
+    path.write_text(data)
+
+if __name__ == '__main__':
+  sys.exit(main(sys.argv[1:]))