Add git diff python tool that outputs file:line in front of diff output.

tools/git/git-diff-ide.py

+#!/usr/bin/env python
+# 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.
+
+"""
+  Invokes git diff [args...] and inserts file:line in front of each line of diff
+  output where possible.
+
+Synopsis:
+  %prog [git diff args...]
+
+Examples:
+  %prog
+  %prog HEAD
+"""
+
+import subprocess
+import sys
+
+
+def GitShell(args, ignore_return=False):
+  """A shell invocation suitable for communicating with git. Returns
+  output as list of lines, raises exception on error.
+  """
+  job = subprocess.Popen(args,
+                         shell=True,
+                         stdout=subprocess.PIPE,
+                         stderr=subprocess.STDOUT)
+  (out, err) = job.communicate()
+  if job.returncode != 0 and not ignore_return:
+    print out
+    raise Exception("Error %d running command %s" % (
+        job.returncode, args))
+  return out.split('\n')
+
+
+def PrintGitDiff(extra_args):
+  """Outputs git diff extra_args with file:line inserted into relevant lines."""
+  current_file = '';
+  line_num = 0;
+  lines = GitShell('git diff %s' % ' '.join(extra_args))
+  for line in lines:
+    if line.startswith('diff ') or \

[Nico, 2012/03/01 21:57:13]

if (foo or
  bar):

is preferred over \

[jbates, 2012/03/01 22:26:00]

Done.

+       line.startswith('index ') or \
+       line.startswith('--- '):
+      print line

[Nico, 2012/03/01 21:57:13]

Maybe it's easier to understand what's going on if you put a comment in each
block describing what the block handles?

E.g.

# Handle:
# diff --git a/third_party/libxml/src/pattern.c
b/third_party/libxml/src/pattern.c
# index 0e38c2d..8cd69ae 100644
# --- a/third_party/libxml/src/pattern.c

[jbates, 2012/03/01 22:26:00]

Done.

+      continue
+    if line.startswith('+++ '):
+      current_file = line[4:] if line[4] == '/' else line[6:]

[Nico, 2012/03/01 21:57:13]

# Handle:
# +++ b/third_party/libxml/src/pattern.c

[jbates, 2012/03/01 22:26:00]

Done.

+      print line
+      continue
+    if line.startswith('@@ '):
+      line_num = int(line.split()[2][1:].split(',')[0])

[Nico, 2012/03/01 21:57:13]

# Handle:
# @@ -305,7 +305,8 @@ xmlNewPatParserContext(const xmlChar *pattern, xmlDictPtr
dict,

Maybe

  _, old_nr, new_nr, _ = line.split(' ', 3)
  line_num = new_nr.split(',')[0]

is a little easier to grok?

[jbates, 2012/03/01 22:26:00]

Done.

+      print line
+      continue
+    print current_file + ':' + repr(line_num) + ':' + line
+    if line.startswith(' ') or line.startswith('+'):
+      line_num += 1
+
+
+def main():
+  PrintGitDiff(sys.argv[1:])
+
+
+if __name__ == '__main__':
+  main()