checkperms: Add a --file-list option.

And use it from //PRESUBMIT.py instead of passing --file <file> for each
file that needs to be processed.

The idea is to read the list of files we want to process from a text file
instead of reading everything from the command-line.

web-platform-test imports were hitting an "argument list too long" error
because there's a particularly huge import with several directories being
renamed; at one point, we ended up with a command-line with ~260k
characters.

Bug: 780055, 780629
Change-Id: Ib1c8b902c42ade77ccbd2662905301d7f766f9d9
Reviewed-on: https://chromium-review.googlesource.com/751504Reviewed-by: Aaron Gable <agable@chromium.org>
Reviewed-by: Dirk Pranke <dpranke@chromium.org>
Reviewed-by: Quinten Yearsley <qyearsley@chromium.org>
Reviewed-by: Daniel Cheng <dcheng@chromium.org>
Commit-Queue: Raphael Kubo da Costa (rakuco) <raphael.kubo.da.costa@intel.com>
Cr-Commit-Position: refs/heads/master@{#515960}

PRESUBMIT.py

@@ -926,16 +926,20 @@ def _CheckFilePermissions(input_api, output_api):
       'tools', 'checkperms', 'checkperms.py')
   args = [input_api.python_executable, checkperms_tool,
           '--root', input_api.change.RepositoryRoot()]
-  for f in input_api.AffectedFiles():
-    # checkperms.py file/directory arguments must be relative to the repository.
-    args += ['--file', f.LocalPath()]
-  try:
-    input_api.subprocess.check_output(args)
-    return []
-  except input_api.subprocess.CalledProcessError as error:
-    return [output_api.PresubmitError(
-        'checkperms.py failed:',
-        long_text=error.output)]
+  with input_api.CreateTemporaryFile() as file_list:
+    for f in input_api.AffectedFiles():
+      # checkperms.py file/directory arguments must be relative to the
+      # repository.
+      file_list.write(f.LocalPath() + '\n')
+    file_list.close()
+    args += ['--file-list', file_list.name]
+    try:
+      input_api.subprocess.check_output(args)
+      return []
+    except input_api.subprocess.CalledProcessError as error:
+      return [output_api.PresubmitError(
+          'checkperms.py failed:',
+          long_text=error.output)]
 
 
 def _CheckTeamTags(input_api, output_api):

tools/checkperms/checkperms.py

@@ -440,6 +440,10 @@ Examples:
       '--file', action='append', dest='files',
       help='Specifics a list of files to check the permissions of. Only these '
       'files will be checked')
+  parser.add_option(
+      '--file-list',
+      help='Specifies a file with a list of files (one per line) to check the '
+      'permissions of. Only these files will be checked')
   parser.add_option('--json', help='Path to JSON output file')
   options, args = parser.parse_args()
 
@@ -449,11 +453,18 @@ Examples:
   if len(args) > 1:
     parser.error('Too many arguments used')
 
+  if options.files and options.file_list:
+    parser.error('--file and --file-list are mutually exclusive options')
+
   if options.root:
     options.root = os.path.abspath(options.root)
 
   if options.files:
     errors = check_files(options.root, options.files)
+  elif options.file_list:
+    with open(options.file_list) as file_list:
+      files = file_list.read().splitlines()
+    errors = check_files(options.root, files)
   else:
     api = get_scm(options.root, options.bare)
     start_dir = args[0] if args else api.root_dir