Preserve raw commit message

Commit messages are now sent to input_api in the exact format that user
has used

Bug: angleproject:4714
Change-Id: I30592aec75d57618f5c028bb63a18f95239976e0
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/tools/depot_tools/+/2239039
Reviewed-by: Edward Lesmes <ehmaldonado@chromium.org>
Commit-Queue: Manh Nguyen <nguyenmh@google.com>

git_cl.py

@@ -902,7 +902,7 @@ def _create_description_from_log(args):
     log_args = [args[0] + '..' + args[1]]
   else:
     log_args = args[:]  # Hope for the best!
-  return RunGit(['log', '--pretty=format:%s%n%n%b'] + log_args)
+  return RunGit(['log', '--pretty=format:%B'] + log_args)
 
 
 class GerritChangeNotExists(Exception):