Add --repackage option to VS packaging script

Sometimes it is necessary to recreate a VS toolchain package with a tiny
change such as editing or removing a single file. Recreating the VS
environment can be time consuming or even impossible (the VS installer
does not allow going to arbitrary versions) so this switch allows
repackaging an existing unpacked directory. The typical usage would be
to make the modifications to one of the toolchain directories in
depot_tools\win_toolchain\vs_files and then repackage it using:

    python package_from_installed.py --repackage third_party\depot_tools\win_toolchain\vs_files\9bc7ccbf9f4bd50d4a3bd185e8ca94ff1618de0b

Bug: 772123
Change-Id: I77b928f695e5f07e33f68dd37711c8761a3c7a22
Reviewed-on: https://chromium-review.googlesource.com/713562
Reviewed-by: Dirk Pranke <dpranke@chromium.org>
Commit-Queue: Bruce Dawson <brucedawson@chromium.org>

win_toolchain/package_from_installed.py

@@ -68,6 +68,19 @@ def ExpandWildcards(root, sub_dir):
   return matches[0]
 
 
+def BuildRepackageFileList(src_dir):
+  # Strip off a trailing slash if present
+  if src_dir.endswith('\\'):
+    src_dir = src_dir[:-1]
+  result = []
+  for root, _, files in os.walk(src_dir):
+    for f in files:
+      final_from = os.path.normpath(os.path.join(root, f))
+      dest = final_from[len(src_dir) + 1:]
+      result.append((final_from, dest))
+  return result
+
+
 def BuildFileList(override_dir):
   result = []
 
@@ -400,8 +413,14 @@ def main():
   parser.add_option('--override', action='store', type='string',
                     dest='override_dir', default=None,
                     help='Specify alternate bin/include/lib directory')
+  parser.add_option('--repackage', action='store', type='string',
+                    dest='repackage_dir', default=None,
+                    help='Specify raw directory to be packaged, for hot fixes.')
   (options, args) = parser.parse_args()
 
+  if options.repackage_dir:
+    files = BuildRepackageFileList(options.repackage_dir)
+  else:
     if len(args) != 1 or args[0] not in ('2015', '2017'):
       print 'Must specify 2015 or 2017'
       parser.print_help();
@@ -449,7 +468,7 @@ def main():
       sys.stdout.write('\r%d/%d ...%s' % (count, len(files), disk_name[-40:]))
       sys.stdout.flush()
       count += 1
-      if disk_name.count(WIN_VERSION) > 0:
+      if not options.repackage_dir and disk_name.count(WIN_VERSION) > 0:
         version_match_count += 1
       if os.path.exists(disk_name):
         if options.dryrun:
@@ -466,7 +485,7 @@ def main():
     return 0
   if missing_files:
     raise Exception('One or more files were missing - aborting')
-  if version_match_count == 0:
+  if not options.repackage_dir and version_match_count == 0:
     raise Exception('No files found that match the specified winversion')
   sys.stdout.write('\rWrote to %s.%s\n' % (output, ' '*50))
   sys.stdout.flush()