[scripts] Add script to fetch clang-format binary from AWS S3 (#33644)

Summary:
**Summary**
This commit adds a script that fetches a platform-appropriate `clang-format` binary
from S3 for use during PyTorch development. The goal is for everyone to use the exact
same `clang-format` binary so that there are no formatting conflicts.

**Testing**
Ran the script.
Pull Request resolved: https://github.com/pytorch/pytorch/pull/33644

Differential Revision: D20076598

Pulled By: SplitInfinity

fbshipit-source-id: cd837076fd30e9c7a8280665c0d652a33b559047

scripts/get_clang_format.py

@@ -0,0 +1,93 @@
+#!/usr/bin/env python
+
+"""Downloads the clang-format binary appropriate for the host platform."""
+
+from __future__ import absolute_import
+from __future__ import division
+from __future__ import print_function
+from __future__ import unicode_literals
+
+import argparse
+import os
+import platform
+import sys
+import urllib.request
+import urllib.error
+
+
+def report_download_progress(chunk_number, chunk_size, file_size):
+    """Pretty printer for file download progress."""
+    if file_size != -1:
+        percent = min(1, (chunk_number * chunk_size) / file_size)
+        bar = "#" * int(64 * percent)
+        sys.stdout.write("\r0% |{:<64}| {}%".format(bar, int(percent * 100)))
+
+
+def download_clang_format(path):
+    """Downloads a clang-format binary appropriate for the host platform and stores it at the given location."""
+    # This dictionary maps each platform to the S3 object URL for its clang-format binary.
+    PLATFORM_TO_URL = {
+        "Darwin": "https://oss-clang-format.s3.us-east-2.amazonaws.com/mac/clang-format-mojave",
+        "Linux": "https://oss-clang-format.s3.us-east-2.amazonaws.com/linux64/clang-format-linux64",
+    }
+
+    plat = platform.system()
+
+    if plat not in PLATFORM_TO_URL:
+        print("Unsupported platform: {}".format(plat))
+        return False
+
+    cf_url = PLATFORM_TO_URL[plat]
+    filename = "{}{}clang-format".format(path, os.sep)
+
+    # Try to download clang-format.
+    try:
+        urllib.request.urlretrieve(
+            cf_url, filename, reporthook=report_download_progress
+        )
+    except urllib.error.URLError as e:
+        print("Error downloading {}: {}".format(filename, str(e)))
+        return False
+    finally:
+        print()
+
+    return True
+
+
+def parse_args(args):
+    """Parse and return command-line arguments."""
+    parser = argparse.ArgumentParser(
+        description="Install a platform-appropriate clang-format binary for use during PyTorch development."
+    )
+    parser.add_argument(
+        "--path", required=True, help="Path where clang-format should be stored"
+    )
+
+    return parser.parse_args(args)
+
+
+def sanitize_path(path):
+    """Sanitize a given path by expanding ~ and converting a relative path to an absolute path."""
+    expand_user = os.path.expanduser(path)
+    abs_path = os.path.abspath(expand_user)
+
+    return abs_path
+
+
+def main(args):
+    # Parse arguments.
+    options = parse_args(args)
+    # Make sure the path is absolute.
+    path = sanitize_path(options.path)
+    # Try downloading clang-format.
+    ok = download_clang_format(path)
+
+    if ok:
+        print("Successfully downloaded clang-format to {}".format(path))
+        print("Remember to add {} to your PATH".format(path))
+
+    return not ok
+
+
+if __name__ == "__main__":
+    sys.exit(main(sys.argv[1:]))