From b7b9728115b5a054bbc908dedfff5208e6957348 Mon Sep 17 00:00:00 2001
From: Nico von Geyso <Nico.Geyso@FU-Berlin.de>
Date: Mon, 6 May 2013 14:41:08 +0200
Subject: [PATCH] support for diffing the empty tree

added missing support for diffing tree-to-tree with NULL as argument.
(see issue #222)
---
 src/tree.c        | 42 +++++++++++++++++++++---------------------
 test/test_diff.py |  6 ++++++
 2 files changed, 27 insertions(+), 21 deletions(-)

diff --git a/src/tree.c b/src/tree.c
index 648b29d..f6a01cf 100644
--- a/src/tree.c
+++ b/src/tree.c
@@ -286,38 +286,38 @@ PyDoc_STRVAR(Tree_diff__doc__,
   "    TODO");
 
 PyObject *
-Tree_diff(Tree *self, PyObject *args)
+Tree_diff(Tree *self, PyObject *args, PyObject *kwds)
 {
     git_diff_options opts = GIT_DIFF_OPTIONS_INIT;
     git_diff_list *diff;
-    int err;
+    git_tree* tree = NULL;
+    git_index* index;
+    git_repository* repo;
+    int err, empty_tree = 0;
+    char *keywords[] = {"obj", "flags", "empty_tree", NULL};
 
     Diff *py_diff;
     PyObject *py_obj = NULL;
 
-    if (!PyArg_ParseTuple(args, "|Oi", &py_obj, &opts.flags))
+    if (!PyArg_ParseTupleAndKeywords(args, kwds, "|Oii", keywords,
+                                     &py_obj, &opts.flags, &empty_tree))
         return NULL;
 
+    repo = self->repo->repo;
     if (py_obj == NULL) {
-        err = git_diff_tree_to_workdir(
-                &diff,
-                self->repo->repo,
-                self->tree,
-                &opts);
+        if (empty_tree > 0)
+            err = git_diff_tree_to_tree(&diff, repo, self->tree, NULL, &opts);
+        else
+            err = git_diff_tree_to_workdir(&diff, repo, self->tree, &opts);
+
     } else if (PyObject_TypeCheck(py_obj, &TreeType)) {
-        err = git_diff_tree_to_tree(
-                &diff,
-                self->repo->repo,
-                self->tree,
-                ((Tree *)py_obj)->tree,
-                &opts);
+        tree = ((Tree *)py_obj)->tree;
+        err = git_diff_tree_to_tree(&diff, repo, self->tree, tree, &opts);
+
     } else if (PyObject_TypeCheck(py_obj, &IndexType)) {
-        err = git_diff_tree_to_index(
-                &diff,
-                self->repo->repo,
-                self->tree,
-                ((Index *)py_obj)->index,
-                &opts);
+        index = ((Index *)py_obj)->index;
+        err = git_diff_tree_to_index(&diff, repo, self->tree, index, &opts);
+
     } else {
         PyErr_SetObject(PyExc_TypeError, py_obj);
         return NULL;
@@ -355,7 +355,7 @@ PyMappingMethods Tree_as_mapping = {
 };
 
 PyMethodDef Tree_methods[] = {
-    METHOD(Tree, diff, METH_VARARGS),
+    METHOD(Tree, diff, METH_VARARGS | METH_KEYWORDS),
     {NULL}
 };
 
diff --git a/test/test_diff.py b/test/test_diff.py
index 71e15cd..c2f514e 100644
--- a/test/test_diff.py
+++ b/test/test_diff.py
@@ -142,6 +142,12 @@ class DiffTest(utils.BareRepoTestCase):
         self.assertEqual(patch.old_file_path, 'a')
         self.assertEqual(patch.new_file_path, 'a')
 
+    def test_diff_empty_tree(self):
+        commit_a = self.repo[COMMIT_SHA1_1]
+        diff = commit_a.tree.diff(empty_tree=True)
+        entries = [p.new_file_path for p in diff]
+        self.assertAll(lambda x: commit_a.tree[x], entries)
+
     def test_diff_tree_opts(self):
         commit_c = self.repo[COMMIT_SHA1_3]
         commit_d = self.repo[COMMIT_SHA1_4]