Allow --3way to be passed to `git apply` via `git cl patch`.

git_cl.py

Index: git_cl.py
diff --git a/git_cl.py b/git_cl.py
index 01fe0767afdb4691e94a121b001e30d50b2239ba..b9012abef86074edee0de21dea6018eea731a469 100755
--- a/git_cl.py
+++ b/git_cl.py
@@ -1693,6 +1693,9 @@ def CMDpatch(parser, args):
                     help='with -b, clobber any existing branch')
   parser.add_option('--reject', action='store_true', dest='reject',
                     help='allow failed patches and spew .rej files')
+  parser.add_option('-3', '--3way', action='store_true', dest='three_way',
+                    help='allow failed patches to fall back on 3-way merge, '
+                        'possibly leaving conflict markers to resolve')
   parser.add_option('-n', '--no-commit', action='store_true', dest='nocommit',
                     help="don't commit after patch applies")
   (options, args) = parser.parse_args(args)
@@ -1750,6 +1753,8 @@ def CMDpatch(parser, args):
   cmd = ['git', '--no-pager', 'apply', '--index', '-p0']
   if options.reject:
     cmd.append('--reject')
+  elif options.three_way:

[M-A Ruel, 2013/06/05 18:47:34]

I'm fine with adding it as the default without an option to disable it. The tool
should return 1 if there is a merge conflict though. Please test it so that git
cl doesn't stack trace here in that case.

+    cmd.append('--3way')
   try:
     subprocess2.check_call(cmd, stdin=patch_data, stdout=subprocess2.VOID)
   except subprocess2.CalledProcessError: