Fix "git cl format" when newer clang-format version is installed.

Fix "git cl format" when newer clang-format version is installed.

Newer versions of clang-format-diff.py now require a -i flag to
explicitely apply edits, otherwise they just print a diff, which
make "git cl format" a no-op.

This patch fixes the issue by probing the script's help text to
see if the flag is needed. If it is, it is added automatically.

BUG=NONE
R=maruel@chromium.org

Committed: http://src.chromium.org/viewvc/chrome?view=rev&revision=231020

[M-A Ruel, 2013-10-25 15:19:09]

https://codereview.chromium.org/44263004/diff/1/git_cl.py
File git_cl.py (right):

https://codereview.chromium.org/44263004/diff/1/git_cl.py#newcode2275
git_cl.py:2275: help_line1 = help_text.split('\n')[0]
if '[-i]' in help_text:
  cmd.append('-i')

assume [-i] was not in previous versions, otherwise use:
if '[-i]' in help_text.splitlines()[0]:
  cmd.append('-i')

[digit1, 2013-10-25 15:25:20]

https://chromiumcodereview.appspot.com/44263004/diff/1/git_cl.py
File git_cl.py (right):

https://chromiumcodereview.appspot.com/44263004/diff/1/git_cl.py#newcode2275
git_cl.py:2275: help_line1 = help_text.split('\n')[0]
Excellent suggestion thanks. I used the first version, since even the official
documentation doesn't mention it. See
http://clang.llvm.org/docs/ClangFormat.html

[M-A Ruel, 2013-10-25 15:26:05]

lgtm

[commit-bot: I haz the power, 2013-10-25 15:34:43]

CQ is trying da patch. Follow status at
https://chromium-status.appspot.com/cq/digit@chromium.org/44263004/60001

[commit-bot: I haz the power, 2013-10-25 15:36:33]

Change committed as 231020