fix(iter-commit): ambiguous argument error

In repositories like

	> git branch -a
	* test
	> ls
	test

`repo.iter_commits` failed due to an ambigous argument
(`'git rev-list test`).
Now this cannot happen anymore.

fixes #264

Author: Byron

git/objects/commit.py

@@ -189,9 +189,12 @@ def iter_items(cls, repo, rev, paths='', **kwargs):
         if 'pretty' in kwargs:
             raise ValueError("--pretty cannot be used as parsing expects single sha's only")
         # END handle pretty
-        args = list()
+
+        # use -- in any case, to prevent possibility of ambiguous arguments
+        # see https://github.com/gitpython-developers/GitPython/issues/264
+        args = ['--']
         if paths:
-            args.extend(('--', paths))
+            args.extend((paths, ))
         # END if paths
 
         proc = repo.git.rev_list(rev, args, as_process=True, **kwargs)

git/test/test_commit.py

@@ -19,15 +19,19 @@
     Actor,
 )
 from gitdb import IStream
+from gitdb.test.lib import with_rw_directory
 from git.compat import (
     string_types,
     text_type
 )
+from git import Repo
+from git.repo.fun import touch
 
 from io import BytesIO
 import time
 import sys
 import re
+import os
 
 
 def assert_commit_serialization(rwrepo, commit_id, print_performance_info=False):
@@ -219,6 +223,15 @@ def test_rev_list_bisect_all(self):
         for sha1, commit in zip(expected_ids, commits):
             assert_equal(sha1, commit.hexsha)
 
+    @with_rw_directory
+    def test_ambiguous_arg_iteration(self, rw_dir):
+        rw_repo = Repo.init(os.path.join(rw_dir, 'test_ambiguous_arg'))
+        path = os.path.join(rw_repo.working_tree_dir, 'master')
+        touch(path)
+        rw_repo.index.add([path])
+        rw_repo.index.commit('initial commit')
+        list(rw_repo.iter_commits(rw_repo.head.ref))  # should fail unless bug is fixed
+
     def test_count(self):
         assert self.rorepo.tag('refs/tags/0.1.5').commit.count() == 143