Fill out diff rename test coverage

This extends the rename tests to make sure that every rename
scenario in the inner loop of git_diff_find_similar is actually
exercised.  Also, fixes an incorrect assert that was in one of
the clauses that was not previously being exercised.

src/diff_tform.c

@@ -776,7 +776,7 @@ int git_diff_find_similar(
 
 				num_rewrites++;
 			} else {
-				assert(delta_is_split(from));
+				assert(delta_is_split(to));
 
 				if (similarity < (int)opts.rename_from_rewrite_threshold)
 					continue;

tests-clar/diff/rename.c

@@ -650,6 +650,58 @@ void test_diff_rename__file_exchange(void)
 	git_buf_free(&c2);
 }
 
+void test_diff_rename__file_partial_exchange(void)
+{
+	git_buf c1 = GIT_BUF_INIT, c2 = GIT_BUF_INIT;
+	git_index *index;
+	git_tree *tree;
+	git_diff_list *diff;
+	git_diff_options diffopts = GIT_DIFF_OPTIONS_INIT;
+	git_diff_find_options opts = GIT_DIFF_FIND_OPTIONS_INIT;
+	diff_expects exp;
+	int i;
+
+	cl_git_pass(git_futils_readbuffer(&c1, "renames/untimely.txt"));
+	cl_git_pass(git_futils_writebuffer(&c1, "renames/songof7cities.txt", 0, 0));
+	for (i = 0; i < 100; ++i)
+		cl_git_pass(git_buf_puts(&c2, "this is not the content you are looking for\n"));
+	cl_git_pass(git_futils_writebuffer(&c2, "renames/untimely.txt", 0, 0));
+
+	cl_git_pass(
+		git_revparse_single((git_object **)&tree, g_repo, "HEAD^{tree}"));
+
+	cl_git_pass(git_repository_index(&index, g_repo));
+	cl_git_pass(git_index_read_tree(index, tree));
+	cl_git_pass(git_index_add_bypath(index, "songof7cities.txt"));
+	cl_git_pass(git_index_add_bypath(index, "untimely.txt"));
+
+	cl_git_pass(git_diff_tree_to_index(&diff, g_repo, tree, index, &diffopts));
+
+	memset(&exp, 0, sizeof(exp));
+	cl_git_pass(git_diff_foreach(
+		diff, diff_file_cb, diff_hunk_cb, diff_line_cb, &exp));
+	cl_assert_equal_i(2, exp.files);
+	cl_assert_equal_i(2, exp.file_status[GIT_DELTA_MODIFIED]);
+
+	opts.flags = GIT_DIFF_FIND_ALL;
+	cl_git_pass(git_diff_find_similar(diff, &opts));
+
+	memset(&exp, 0, sizeof(exp));
+	cl_git_pass(git_diff_foreach(
+		diff, diff_file_cb, diff_hunk_cb, diff_line_cb, &exp));
+	cl_assert_equal_i(3, exp.files);
+	cl_assert_equal_i(1, exp.file_status[GIT_DELTA_RENAMED]);
+	cl_assert_equal_i(1, exp.file_status[GIT_DELTA_ADDED]);
+	cl_assert_equal_i(1, exp.file_status[GIT_DELTA_DELETED]);
+
+	git_diff_list_free(diff);
+	git_tree_free(tree);
+	git_index_free(index);
+
+	git_buf_free(&c1);
+	git_buf_free(&c2);
+}
+
 void test_diff_rename__file_split(void)
 {
 	git_buf c1 = GIT_BUF_INIT, c2 = GIT_BUF_INIT;
@@ -706,3 +758,56 @@ void test_diff_rename__file_split(void)
 	git_buf_free(&c1);
 	git_buf_free(&c2);
 }
+
+void test_diff_rename__from_deleted_to_split(void)
+{
+	git_buf c1 = GIT_BUF_INIT;
+	git_index *index;
+	git_tree *tree;
+	git_diff_list *diff;
+	git_diff_options diffopts = GIT_DIFF_OPTIONS_INIT;
+	git_diff_find_options opts = GIT_DIFF_FIND_OPTIONS_INIT;
+	diff_expects exp;
+
+	/* old file is missing, new file is actually old file renamed */
+
+	cl_git_pass(git_futils_readbuffer(&c1, "renames/songof7cities.txt"));
+	cl_git_pass(git_futils_writebuffer(&c1, "renames/untimely.txt", 0, 0));
+
+	cl_git_pass(
+		git_revparse_single((git_object **)&tree, g_repo, "HEAD^{tree}"));
+
+	cl_git_pass(git_repository_index(&index, g_repo));
+	cl_git_pass(git_index_read_tree(index, tree));
+	cl_git_pass(git_index_remove_bypath(index, "songof7cities.txt"));
+	cl_git_pass(git_index_add_bypath(index, "untimely.txt"));
+
+	diffopts.flags = GIT_DIFF_INCLUDE_UNMODIFIED;
+
+	cl_git_pass(git_diff_tree_to_index(&diff, g_repo, tree, index, &diffopts));
+
+	memset(&exp, 0, sizeof(exp));
+	cl_git_pass(git_diff_foreach(
+		diff, diff_file_cb, diff_hunk_cb, diff_line_cb, &exp));
+	cl_assert_equal_i(4, exp.files);
+	cl_assert_equal_i(1, exp.file_status[GIT_DELTA_DELETED]);
+	cl_assert_equal_i(1, exp.file_status[GIT_DELTA_MODIFIED]);
+	cl_assert_equal_i(2, exp.file_status[GIT_DELTA_UNMODIFIED]);
+
+	opts.flags = GIT_DIFF_FIND_ALL;
+	cl_git_pass(git_diff_find_similar(diff, &opts));
+
+	memset(&exp, 0, sizeof(exp));
+	cl_git_pass(git_diff_foreach(
+		diff, diff_file_cb, diff_hunk_cb, diff_line_cb, &exp));
+	cl_assert_equal_i(4, exp.files);
+	cl_assert_equal_i(1, exp.file_status[GIT_DELTA_DELETED]);
+	cl_assert_equal_i(1, exp.file_status[GIT_DELTA_RENAMED]);
+	cl_assert_equal_i(2, exp.file_status[GIT_DELTA_UNMODIFIED]);
+
+	git_diff_list_free(diff);
+	git_tree_free(tree);
+	git_index_free(index);
+
+	git_buf_free(&c1);
+}