Attempt at making git-drover work on Windows

git_drover.py

 #!/usr/bin/env python
 # Copyright 2015 The Chromium Authors. All rights reserved.
 # Use of this source code is governed by a BSD-style license that can be
 # found in the LICENSE file.
 """git drover: A tool for merging changes to release branches."""
 
 import argparse
 import functools
 import logging
 import os
 import shutil
 import subprocess
 import sys
 import tempfile
 
 import git_common
 
 
 class Error(Exception):
   pass
 
 
+if os.name == 'nt':
+  # This is a just-good-enough emulation of os.symlink for drover to work on
+  # Windows. It uses junctioning of directories (most of the contents of
+  # the .git directory), but copies files. Note that we can't use
+  # CreateSymbolicLink or CreateHardLink here, as they both require elevation.
+  # Creating reparse points is what we want for the directories, but doing so
+  # is a relatively messy set of DeviceIoControl work at the API level, so we
+  # simply shell to `mklink /j` instead.
+  def emulate_symlink_windows(source, link_name):
+    if os.path.isdir(source):
+      subprocess.check_call(['mklink', '/j',
+                             link_name.replace('/', '\\'),
+                             source.replace('/', '\\')],
+                            shell=True)
+    else:
+      shutil.copy(source, link_name)
+  os.symlink = emulate_symlink_windows

[iannucci, 2015/10/07 22:58:26]

Though I'm not totally sold on adding this back into os

Maybe do

if 'nt':
  mk_symlink = shell to mklink
else:
  mk_symlink = os.symlink

?

[scottmg, 2015/10/07 23:03:52]

It sort of has to be os.symlink, or else various code in git_common.py code
needs to be changed.

I didn't really digest Primiano's message
https://groups.google.com/a/chromium.org/d/msg/chromium-dev/uVQt89p9ZY0/NZI_6...,
but it sounds like there's a better way than symlinks now anyway? So maybe we
should do this for now and then replace the symlink with alternates later.

+
+
 class _Drover(object):
 
   def __init__(self, branch, revision, parent_repo, dry_run):
     self._branch = branch
     self._branch_ref = 'refs/remotes/branch-heads/%s' % branch
     self._revision = revision
     self._parent_repo = os.path.abspath(parent_repo)
     self._dry_run = dry_run
     self._workdir = None
     self._branch_name = None
@@ skipping 32 matching lines @@
   def _cleanup(self):
     if self._branch_name:
       try:
         self._run_git_command(['cherry-pick', '--abort'])
       except Error:
         pass
       self._run_git_command(['checkout', '--detach'])
       self._run_git_command(['branch', '-D', self._branch_name])
     if self._workdir:
       logging.debug('Deleting %s', self._workdir)
-      shutil.rmtree(self._workdir)
+      if os.name == 'nt':
+        # Use rmdir to properly handle the junctions we created.
+        subprocess.check_call(['rmdir', '/s', '/q', self._workdir], shell=True)
+      else:
+        shutil.rmtree(self._workdir)
     self._dev_null_file.close()
 
   @staticmethod
   def _confirm(message):
     """Show a confirmation prompt with the given message.
 
     Returns:
       A bool representing whether the user wishes to continue.
     """
     result = ''
@@ skipping 159 matching lines @@
   try:
     cherry_pick_change(options.branch, options.cherry_pick,
                        options.parent_checkout, options.dry_run)
   except Error as e:
     logging.error(e.message)
     sys.exit(128)
 
 
 if __name__ == '__main__':
   main()