[bootstrap] Move bitness detection logic into Python

Bug: 703064

Change-Id: I319e89a43533b86c0eedff56fec2665fa13e728c
Reviewed-on: https://chromium-review.googlesource.com/466006
Commit-Queue: Robbie Iannucci <iannucci@chromium.org>
Reviewed-by: Robbie Iannucci <iannucci@chromium.org>

bootstrap/win/git_bootstrap.py

@@ -6,6 +6,7 @@ import argparse
 import fnmatch
 import logging
 import os
+import platform
 import shutil
 import subprocess
 import sys
@@ -26,6 +27,11 @@ def _check_call(argv, **kwargs):
   subprocess.check_call(argv, **kwargs)
 
 
+def get_os_bitness():
+  """Returns bitness of operating system as int."""
+  return 64 if platform.machine().endswith('64') else 32
+
+
 def get_target_git_version():
   """Returns git version that should be installed."""
   if os.path.exists(os.path.join(ROOT_DIR, '.git_bleeding_edge')):
@@ -148,8 +154,9 @@ def install_git(args, git_version, git_directory):
 
 def main(argv):
   parser = argparse.ArgumentParser()
-  parser.add_argument('--bits', type=int, choices=(32,64), default=64,
-                      help='Bitness of the client to install.')
+  parser.add_argument('--bits', type=int, choices=(32,64),
+                      help='Bitness of the client to install. Default on this'
+                      ' system: %(default)s', default=get_os_bitness())
   parser.add_argument('--cipd-client',
                       help='Path to CIPD client binary. default: %(default)s',
                       default=os.path.join(ROOT_DIR, 'cipd'+BAT_EXT))

bootstrap/win/win_tools.bat

@@ -58,16 +58,7 @@ set ERRORLEVEL=1
 goto :END
 
 :GIT_CHECK
-
-:: must explicitly use FIND_EXE to prevent this from grabbing e.g. gnuwin32 or
-:: msys versions.
-set FIND_EXE=%SYSTEMROOT%\System32\find.exe
-
-:: Check to see if we're on a 32 or 64 bit system
-:: (parens) are necessary, otherwise batch puts an extra space after 32.
-reg Query "HKLM\Hardware\Description\System\CentralProcessor\0" | %FIND_EXE% /i "x86" > NUL && (set OS_BITS=32) || (set OS_BITS=64)
-
-"%WIN_TOOLS_ROOT_DIR%\python.bat" "%~dp0git_bootstrap.py" --bits "%OS_BITS%"
+"%WIN_TOOLS_ROOT_DIR%\python.bat" "%~dp0git_bootstrap.py"
 goto :END
 
 :returncode