thodg/libgit2

diff --git a/include/git2/checkout.h b/include/git2/checkout.h
index 3217ac9..5707de0 100644
--- a/include/git2/checkout.h
+++ b/include/git2/checkout.h
@@ -21,13 +21,16 @@
  */
 GIT_BEGIN_DECL
 
-
-#define GIT_CHECKOUT_OVERWRITE_EXISTING 0 /* default */
-#define GIT_CHECKOUT_SKIP_EXISTING 1
+enum {
+	GIT_CHECKOUT_DEFAULT			= (1 << 0),
+	GIT_CHECKOUT_OVERWRITE_MODIFIED	= (1 << 1),
+	GIT_CHECKOUT_CREATE_MISSING		= (1 << 2),
+	GIT_CHECKOUT_REMOVE_UNTRACKED	= (1 << 3),
+};
 
 /* Use zeros to indicate default settings */
 typedef struct git_checkout_opts {
-	int existing_file_action; /* default: GIT_CHECKOUT_OVERWRITE_EXISTING */
+	unsigned int checkout_strategy; /* default: GIT_CHECKOUT_DEFAULT */
 	int disable_filters;
 	int dir_mode; /* default is 0755 */
 	int file_mode; /* default is 0644 */
diff --git a/src/checkout.c b/src/checkout.c
index 6e34e50..beb8b5a 100644
--- a/src/checkout.c
+++ b/src/checkout.c
@@ -143,6 +143,9 @@ static int checkout_diff_fn(
 
 	switch (delta->status) {
 	case GIT_DELTA_UNTRACKED:
+		if (!(data->checkout_opts->checkout_strategy & GIT_CHECKOUT_REMOVE_UNTRACKED))
+			return 0;
+
 		if (!git__suffixcmp(delta->new_file.path, "/"))
 			error = git_futils_rmdir_r(git_buf_cstr(data->path), GIT_DIRREMOVAL_FILES_AND_DIRS);
 		else
@@ -150,11 +153,24 @@ static int checkout_diff_fn(
 		break;
 
 	case GIT_DELTA_MODIFIED:
-		/* Deal with pre-existing files */
-		if (data->checkout_opts->existing_file_action == GIT_CHECKOUT_SKIP_EXISTING)
+		if (!(data->checkout_opts->checkout_strategy & GIT_CHECKOUT_OVERWRITE_MODIFIED))
 			return 0;
 
+		if (checkout_blob(
+				data->owner,
+				&delta->old_file.oid,
+				git_buf_cstr(data->path),
+				delta->old_file.mode,
+				data->can_symlink,
+				data->checkout_opts) < 0)
+			goto cleanup;
+
+		break;
+
 	case GIT_DELTA_DELETED:
+		if (!(data->checkout_opts->checkout_strategy & GIT_CHECKOUT_CREATE_MISSING))
+			return 0;
+
 		if (checkout_blob(
 				data->owner,
 				&delta->old_file.oid,
@@ -209,8 +225,8 @@ static void normalize_options(git_checkout_opts *normalized, git_checkout_opts *
 		memmove(normalized, proposed, sizeof(git_checkout_opts));
 
 	/* Default options */
-	if (!normalized->existing_file_action)
-		normalized->existing_file_action = GIT_CHECKOUT_OVERWRITE_EXISTING;
+	if (!normalized->checkout_strategy)
+		normalized->checkout_strategy = GIT_CHECKOUT_DEFAULT;
 
 	/* opts->disable_filters is false by default */
 	if (!normalized->dir_mode)
diff --git a/src/reset.c b/src/reset.c
index efe3b6b..4ce21e2 100644
--- a/src/reset.c
+++ b/src/reset.c
@@ -28,6 +28,7 @@ int git_reset(
 	git_index *index = NULL;
 	git_tree *tree = NULL;
 	int error = -1;
+	git_checkout_opts opts;
 
 	assert(repo && target);
 	assert(reset_type == GIT_RESET_SOFT
@@ -81,7 +82,13 @@ int git_reset(
 		goto cleanup;
 	}
 
-	if (git_checkout_index(repo, NULL, NULL, NULL) < 0) {
+	memset(&opts, 0, sizeof(opts));
+	opts.checkout_strategy =
+		GIT_CHECKOUT_CREATE_MISSING
+		| GIT_CHECKOUT_OVERWRITE_MODIFIED
+		| GIT_CHECKOUT_REMOVE_UNTRACKED;
+
+	if (git_checkout_index(repo, &opts, NULL) < 0) {
 		giterr_set(GITERR_INDEX, "%s - Failed to checkout the index.", ERROR_MSG);
 		goto cleanup;
 	}
diff --git a/tests-clar/checkout/index.c b/tests-clar/checkout/index.c
index b81aa91..fad10be 100644
--- a/tests-clar/checkout/index.c
+++ b/tests-clar/checkout/index.c
@@ -26,6 +26,7 @@ void test_checkout_index__initialize(void)
 	git_tree *tree;
 
 	memset(&g_opts, 0, sizeof(g_opts));
+	g_opts.checkout_strategy = GIT_CHECKOUT_CREATE_MISSING;
 
 	g_repo = cl_git_sandbox_init("testrepo");
 
@@ -71,19 +72,34 @@ void test_checkout_index__cannot_checkout_a_bare_repository(void)
 	cl_git_fail(git_checkout_index(g_repo, NULL, NULL));
 }
 
-void test_checkout_index__update_the_content_of_workdir_with_missing_files(void)
+void test_checkout_index__can_create_missing_files(void)
 {
 	cl_assert_equal_i(false, git_path_isfile("./testrepo/README"));
 	cl_assert_equal_i(false, git_path_isfile("./testrepo/branch_file.txt"));
 	cl_assert_equal_i(false, git_path_isfile("./testrepo/new.txt"));
 
-	cl_git_pass(git_checkout_index(g_repo, NULL, NULL));
+	g_opts.checkout_strategy = GIT_CHECKOUT_CREATE_MISSING;
+	cl_git_pass(git_checkout_index(g_repo, &g_opts, NULL));
 
 	test_file_contents("./testrepo/README", "hey there\n");
 	test_file_contents("./testrepo/branch_file.txt", "hi\nbye!\n");
 	test_file_contents("./testrepo/new.txt", "my new file\n");
 }
 
+void test_checkout_index__can_remove_untracked_files(void)
+{
+	git_futils_mkdir("./testrepo/dir/subdir/subsubdir", NULL, 0755, GIT_MKDIR_PATH);
+	cl_git_mkfile("./testrepo/dir/one", "one\n");
+	cl_git_mkfile("./testrepo/dir/subdir/two", "two\n");
+
+	cl_assert_equal_i(true, git_path_isdir("./testrepo/dir/subdir/subsubdir"));
+
+	g_opts.checkout_strategy = GIT_CHECKOUT_REMOVE_UNTRACKED;
+	cl_git_pass(git_checkout_index(g_repo, &g_opts, NULL));
+
+	cl_assert_equal_i(false, git_path_isdir("./testrepo/dir"));
+}
+
 void test_checkout_index__honor_the_specified_pathspecs(void)
 {
 	git_strarray paths;
@@ -128,7 +144,7 @@ void test_checkout_index__honor_the_gitattributes_directives(void)
 	cl_git_mkfile("./testrepo/.gitattributes", attributes);
 	set_core_autocrlf_to(false);
 
-	cl_git_pass(git_checkout_index(g_repo, NULL, NULL));
+	cl_git_pass(git_checkout_index(g_repo, &g_opts, NULL));
 
 	test_file_contents("./testrepo/README", "hey there\n");
 	test_file_contents("./testrepo/new.txt", "my new file\n");
@@ -143,7 +159,7 @@ void test_checkout_index__honor_coreautocrlf_setting_set_to_true(void)
 	cl_git_pass(p_unlink("./testrepo/.gitattributes"));
 	set_core_autocrlf_to(true);
 
-	cl_git_pass(git_checkout_index(g_repo, NULL, NULL));
+	cl_git_pass(git_checkout_index(g_repo, &g_opts, NULL));
 
 	test_file_contents("./testrepo/README", expected_readme_text);
 #endif
@@ -158,7 +174,7 @@ void test_checkout_index__honor_coresymlinks_setting_set_to_true(void)
 {
 	set_repo_symlink_handling_cap_to(true);
 
-	cl_git_pass(git_checkout_index(g_repo, NULL, NULL));
+	cl_git_pass(git_checkout_index(g_repo, &g_opts, NULL));
 
 #ifdef GIT_WIN32
 	test_file_contents("./testrepo/link_to_new.txt", "new.txt");
@@ -180,26 +196,26 @@ void test_checkout_index__honor_coresymlinks_setting_set_to_false(void)
 {
 	set_repo_symlink_handling_cap_to(false);
 
-	cl_git_pass(git_checkout_index(g_repo, NULL, NULL));
+	cl_git_pass(git_checkout_index(g_repo, &g_opts, NULL));
 
 	test_file_contents("./testrepo/link_to_new.txt", "new.txt");
 }
 
-void test_checkout_index__options_skip_existing_file(void)
+void test_checkout_index__donot_overwrite_modified_file_by_default(void)
 {
 	cl_git_mkfile("./testrepo/new.txt", "This isn't what's stored!");
-	g_opts.existing_file_action = GIT_CHECKOUT_SKIP_EXISTING;
 
+	g_opts.checkout_strategy = 0;
 	cl_git_pass(git_checkout_index(g_repo, &g_opts, NULL));
 
 	test_file_contents("./testrepo/new.txt", "This isn't what's stored!");
 }
 
-void test_checkout_index__options_overwrite_existing_file(void)
+void test_checkout_index__can_overwrite_modified_file(void)
 {
 	cl_git_mkfile("./testrepo/new.txt", "This isn't what's stored!");
-	g_opts.existing_file_action = GIT_CHECKOUT_OVERWRITE_EXISTING;
 
+	g_opts.checkout_strategy = GIT_CHECKOUT_OVERWRITE_MODIFIED;
 	cl_git_pass(git_checkout_index(g_repo, &g_opts, NULL));
 
 	test_file_contents("./testrepo/new.txt", "my new file\n");
@@ -267,6 +283,8 @@ void test_checkout_index__options_open_flags(void)
 	cl_git_mkfile("./testrepo/new.txt", "hi\n");
 
 	g_opts.file_open_flags = O_CREAT | O_RDWR | O_APPEND;
+
+	g_opts.checkout_strategy |= GIT_CHECKOUT_OVERWRITE_MODIFIED;
 	cl_git_pass(git_checkout_index(g_repo, &g_opts, NULL));
 
 	test_file_contents("./testrepo/new.txt", "hi\nmy new file\n");