update-manpages: include in unittests

People often forget to regen when making interface changes.

We skip the test if help2man isn't installed since it's not common,
and it's not available on our CI bots currently.

Change-Id: Ib4911a0e3fa1294ad90e4ac8afc047a0b7c2b66d
Reviewed-on: https://gerrit-review.googlesource.com/c/git-repo/+/469741
Tested-by: Mike Frysinger <vapier@google.com>
Reviewed-by: Gavin Mak <gavinmak@google.com>
Commit-Queue: Mike Frysinger <vapier@google.com>

release/update_manpages.py

@@ -27,9 +27,11 @@ import shutil
 import subprocess
 import sys
 import tempfile
+from typing import List
 
 
-TOPDIR = Path(__file__).resolve().parent.parent
+THIS_FILE = Path(__file__).resolve()
+TOPDIR = THIS_FILE.parent.parent
 MANDIR = TOPDIR.joinpath("man")
 
 # Load repo local modules.
@@ -42,9 +44,23 @@ def worker(cmd, **kwargs):
     subprocess.run(cmd, **kwargs)
 
 
-def main(argv):
+def get_parser() -> argparse.ArgumentParser:
+    """Get argument parser."""
     parser = argparse.ArgumentParser(description=__doc__)
-    parser.parse_args(argv)
+    parser.add_argument(
+        "-n",
+        "--check",
+        "--dry-run",
+        action="store_const",
+        const=True,
+        help="Check if changes are necessary; don't actually change files",
+    )
+    return parser
+
+
+def main(argv: List[str]) -> int:
+    parser = get_parser()
+    opts = parser.parse_args(argv)
 
     if not shutil.which("help2man"):
         sys.exit("Please install help2man to continue.")
@@ -117,6 +133,7 @@ def main(argv):
                 functools.partial(worker, cwd=tempdir, check=True), cmdlist
             )
 
+    ret = 0
     for tmp_path in MANDIR.glob("*.1.tmp"):
         path = tmp_path.parent / tmp_path.stem
         old_data = path.read_text() if path.exists() else ""
@@ -133,7 +150,17 @@ def main(argv):
         )
         new_data = re.sub(r'^(\.TH REPO "1" ")([^"]+)', r"\1", data, flags=re.M)
         if old_data != new_data:
-            path.write_text(data)
+            if opts.check:
+                ret = 1
+                print(
+                    f"{THIS_FILE.name}: {path.name}: "
+                    "man page needs regenerating",
+                    file=sys.stderr,
+                )
+            else:
+                path.write_text(data)
+
+    return ret
 
 
 def replace_regex(data):