Add option to specify similarity level for git diff operations on commandline

tests/git_cl_test.py

Index: tests/git_cl_test.py
diff --git a/tests/git_cl_test.py b/tests/git_cl_test.py
index f02465db9e74a7014db6ad1be382689494ee3177..9667a1461335548714ee9b5c88209cab117e7cc3 100755
--- a/tests/git_cl_test.py
+++ b/tests/git_cl_test.py
@@ -115,7 +115,7 @@ class TestGitCl(TestCase):
       ((['git', 'log', '--pretty=format:%s%n%n%b', 'master...'],), 'foo'),
       ((['git', 'config', 'user.email'],), 'me@example.com'),
       ((['git', 'diff', '--no-ext-diff', '--stat', '--find-copies-harder',
-         '-l100000', 'master...'],),
+         '-C50', '-l100000', 'master...'],),
        '+dat'),
       ((['git', 'log', '--pretty=format:%s\n\n%b', 'master..'],), 'desc\n'),
     ]
@@ -193,7 +193,8 @@ class TestGitCl(TestCase):
   def _dcommit_calls_3(cls):
     return [
       ((['git', 'diff', '--no-ext-diff', '--stat', '--find-copies-harder',
-         '-l100000', 'refs/remotes/origin/master', 'refs/heads/working'],),
+         '-C50', '-l100000', 'refs/remotes/origin/master',
+         'refs/heads/working'],),
        (' PRESUBMIT.py |    2 +-\n'
         ' 1 files changed, 1 insertions(+), 1 deletions(-)\n')),
       (('About to commit; enter to confirm.',), None),
@@ -209,7 +210,8 @@ class TestGitCl(TestCase):
       ((['git', 'commit', '-m',
          'Issue: 12345\n\nReview URL: https://codereview.example.com/12345'],),
        ''),
-      ((['git', 'svn', 'dcommit', '--no-rebase', '--rmdir'],), (('', None), 0)),
+      ((['git', 'svn', 'dcommit', '-C50', '--no-rebase', '--rmdir'],),
+       (('', None), 0)),
       ((['git', 'checkout', '-q', 'working'],), ''),
       ((['git', 'branch', '-D', 'git-cl-commit'],), ''),
   ]
@@ -223,6 +225,7 @@ class TestGitCl(TestCase):
         '--message', description
     ] + args + [
         '--cc', 'joe@example.com',
+        '--git_similarity', '50',
         'master...'
     ]
 
@@ -354,7 +357,7 @@ class TestGitCl(TestCase):
         ((['git', 'log', '--pretty=format:%s%n%n%b', 'master...'],), 'foo'),
         ((['git', 'config', 'user.email'],), 'me@example.com'),
         ((['git', 'diff', '--no-ext-diff', '--stat', '--find-copies-harder',
-           '-l100000', 'master...'],),
+           '-C50', '-l100000', 'master...'],),
          '+dat'),
         ]