fix(index):allow adding non-unicode paths to index

This issue only surfaced in python 2, in case paths containing unicode
characters were not actual unicode objects.

In python 3, this was never the issue.

Closes gitpython-developers#331

Author: Byron

git/index/fun.py

@@ -41,7 +41,8 @@
 from gitdb.typ import str_tree_type
 from git.compat import (
     defenc,
-    force_text
+    force_text,
+    force_bytes
 )
 
 S_IFGITLINK = S_IFLNK | S_IFDIR     # a submodule
@@ -124,7 +125,7 @@ def write_cache(entries, stream, extension_data=None, ShaStreamCls=IndexFileSHA1
         write(entry[4])         # ctime
         write(entry[5])         # mtime
         path = entry[3]
-        path = path.encode(defenc)
+        path = force_bytes(path, encoding=defenc)
         plen = len(path) & CE_NAMEMASK      # path length
         assert plen == len(path), "Path %s too long to fit into index" % entry[3]
         flags = plen | (entry[2] & CE_NAMEMASK_INV)     # clear possible previous values

git/test/test_index.py

@@ -18,6 +18,7 @@
 )
 from git import (
     IndexFile,
+    Repo,
     BlobFilter,
     UnmergedEntriesError,
     Tree,
@@ -45,6 +46,7 @@
     IndexEntry
 )
 from git.index.fun import hook_path
+from gitdb.test.lib import with_rw_directory
 
 
 class TestIndex(TestBase):
@@ -780,3 +782,14 @@ def test_index_bare_add(self, rw_bare_repo):
         except InvalidGitRepositoryError:
             asserted = True
         assert asserted, "Adding using a filename is not correctly asserted."
+
+    @with_rw_directory
+    def test_add_utf8P_path(self, rw_dir):
+        # NOTE: fp is not a Unicode object in python 2 (which is the source of the problem)
+        fp = os.path.join(rw_dir, 'ø.txt')
+        with open(fp, 'w') as fs:
+            fs.write('content of ø')
+
+        r = Repo.init(rw_dir)
+        r.index.add([fp])
+        r.index.commit('Added orig and prestable')