Improve the diagnostics for include order presubmit checks

PRESUBMIT.py

 # Copyright (c) 2012 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.
 
 """Top-level presubmit script for Chromium.
 
 See http://dev.chromium.org/developers/how-tos/depottools/presubmit-scripts
 for more details about the presubmit API built into depot_tools.
 """
 
@@ skipping 45 matching lines @@
 
 _TEST_ONLY_WARNING = (
     'You might be calling functions intended only for testing from\n'
     'production code.  It is OK to ignore this warning if you know what\n'
     'you are doing, as the heuristics used to detect the situation are\n'
     'not perfect.  The commit queue will not block on this warning.')
 
 
 _INCLUDE_ORDER_WARNING = (
     'Your #include order seems to be broken. Remember to use the right '
-    'collation (LC_COLLATE=C) and check https://google-styleguide.googlecode'
+    'collation (LC_COLLATE=C) and check\nhttps://google-styleguide.googlecode'
     '.com/svn/trunk/cppguide.html#Names_and_Order_of_Includes')
 
 _BANNED_OBJC_FUNCTIONS = (
     (
       'addTrackingRect:',
       (
        'The use of -[NSView addTrackingRect:owner:userData:assumeInside:] is'
        'prohibited. Please use CrTrackingArea instead.',
        'http://dev.chromium.org/developers/coding-style/cocoa-dos-and-donts',
       ),
@@ skipping 618 matching lines @@
   cpp_system_include_pattern = input_api.re.compile(r'\s*#include <.*>')
   custom_include_pattern = input_api.re.compile(r'\s*#include ".*')
 
   C_SYSTEM_INCLUDES, CPP_SYSTEM_INCLUDES, CUSTOM_INCLUDES = range(3)
 
   state = C_SYSTEM_INCLUDES
 
   previous_line = ''
   previous_line_num = 0
   problem_linenums = []
+  out_of_order = " - line belongs before previous line"
   for line_num, line in scope:
     if c_system_include_pattern.match(line):
       if state != C_SYSTEM_INCLUDES:
-        problem_linenums.append((line_num, previous_line_num))
+        problem_linenums.append((line_num, previous_line_num,
+            " - C system include file in wrong block"))
       elif previous_line and previous_line > line:
-        problem_linenums.append((line_num, previous_line_num))
+        problem_linenums.append((line_num, previous_line_num,
+            out_of_order))
     elif cpp_system_include_pattern.match(line):
       if state == C_SYSTEM_INCLUDES:
         state = CPP_SYSTEM_INCLUDES
       elif state == CUSTOM_INCLUDES:
-        problem_linenums.append((line_num, previous_line_num))
+        problem_linenums.append((line_num, previous_line_num,
+            " - c++ system include file in wrong block"))
       elif previous_line and previous_line > line:
-        problem_linenums.append((line_num, previous_line_num))
+        problem_linenums.append((line_num, previous_line_num, out_of_order))
     elif custom_include_pattern.match(line):
       if state != CUSTOM_INCLUDES:
         state = CUSTOM_INCLUDES
       elif previous_line and previous_line > line:
-        problem_linenums.append((line_num, previous_line_num))
+        problem_linenums.append((line_num, previous_line_num, out_of_order))
     else:
-      problem_linenums.append(line_num)
+      problem_linenums.append((line_num, previous_line_num,
+          "Unknown include type"))
     previous_line = line
     previous_line_num = line_num
 
   warnings = []
-  for (line_num, previous_line_num) in problem_linenums:
+  for (line_num, previous_line_num, failure_type) in problem_linenums:
     if line_num in changed_linenums or previous_line_num in changed_linenums:
-      warnings.append('    %s:%d' % (file_path, line_num))
+      warnings.append('    %s:%d:%s' % (file_path, line_num, failure_type))
   return warnings
 
 
 def _CheckIncludeOrderInFile(input_api, f, changed_linenums):
   """Checks the #include order for the given file f."""
 
   system_include_pattern = input_api.re.compile(r'\s*#include \<.*')
   # Exclude the following includes from the check:
   # 1) #include <.../...>, e.g., <sys/...> includes often need to appear in a
   # specific order.
@@ skipping 1132 matching lines @@
   for master in masters:
     try_config.setdefault(master, {})
     for builder in masters[master]:
       # Do not trigger presubmit builders, since they're likely to fail
       # (e.g. OWNERS checks before finished code review), and we're
       # running local presubmit anyway.
       if 'presubmit' not in builder:
         try_config[master][builder] = ['defaulttests']
 
   return try_config