Adding upstream version 1.7.2+ds.upstream/1.7.2+ds

Signed-off-by: Daniel Baumann <daniel.baumann@progress-linux.org>

22 files changed, 2756 insertions, 0 deletions

diff --git a/src/cli/CMakeLists.txt b/src/cli/CMakeLists.txt
new file mode 100644
index 0000000..84b6c19
--- /dev/null
+++ b/src/cli/CMakeLists.txt
@@ -0,0 +1,56 @@
+set(CLI_INCLUDES
+	"${libgit2_BINARY_DIR}/src/util"
+	"${libgit2_BINARY_DIR}/include"
+	"${libgit2_SOURCE_DIR}/src/util"
+	"${libgit2_SOURCE_DIR}/src/cli"
+	"${libgit2_SOURCE_DIR}/include"
+	"${LIBGIT2_DEPENDENCY_INCLUDES}")
+
+if(WIN32 AND NOT CYGWIN)
+	file(GLOB CLI_SRC_OS win32/*.c)
+	list(SORT CLI_SRC_OS)
+else()
+	file(GLOB CLI_SRC_OS unix/*.c)
+	list(SORT CLI_SRC_OS)
+endif()
+
+file(GLOB CLI_SRC_C *.c *.h)
+list(SORT CLI_SRC_C)
+
+#
+# The CLI currently needs to be statically linked against libgit2 because
+# the utility library uses libgit2's thread-local error buffers.  TODO:
+# remove this dependency and allow us to dynamically link against libgit2.
+#
+
+if(BUILD_CLI STREQUAL "dynamic")
+	set(CLI_LIBGIT2_LIBRARY libgit2package)
+else()
+	set(CLI_LIBGIT2_OBJECTS $<TARGET_OBJECTS:libgit2>)
+endif()
+
+#
+# Compile and link the CLI
+#
+
+add_executable(git2_cli ${CLI_SRC_C} ${CLI_SRC_OS} ${CLI_OBJECTS}
+	$<TARGET_OBJECTS:util>
+	${CLI_LIBGIT2_OBJECTS}
+	${LIBGIT2_DEPENDENCY_OBJECTS})
+target_link_libraries(git2_cli ${CLI_LIBGIT2_LIBRARY} ${LIBGIT2_SYSTEM_LIBS})
+
+set_target_properties(git2_cli PROPERTIES C_STANDARD 90)
+set_target_properties(git2_cli PROPERTIES RUNTIME_OUTPUT_DIRECTORY ${libgit2_BINARY_DIR})
+set_target_properties(git2_cli PROPERTIES OUTPUT_NAME ${LIBGIT2_FILENAME})
+
+ide_split_sources(git2_cli)
+
+target_include_directories(git2_cli PRIVATE ${CLI_INCLUDES})
+
+if(MSVC_IDE)
+	# Precompiled headers
+	set_target_properties(git2_cli PROPERTIES COMPILE_FLAGS "/Yuprecompiled.h /FIprecompiled.h")
+	set_source_files_properties(win32/precompiled.c COMPILE_FLAGS "/Ycprecompiled.h")
+endif()
+
+install(TARGETS git2_cli RUNTIME DESTINATION ${CMAKE_INSTALL_BINDIR})
diff --git a/src/cli/README.md b/src/cli/README.md
new file mode 100644
index 0000000..3087c39
--- /dev/null
+++ b/src/cli/README.md
@@ -0,0 +1,26 @@
+# cli
+
+A git-compatible command-line interface that uses libgit2.
+
+## Adding commands
+
+1. Individual commands have a `main`-like top-level entrypoint.  For example:
+
+   ```c
+   int cmd_help(int argc, char **argv)
+   ```
+
+   Although this is the same signature as `main`, commands are not built as
+   individual standalone executables, they'll be linked into the main cli.
+   (Though there may be an option for command executables to be built as
+   standalone executables in the future.)
+
+2. Commands are prototyped in `cmd.h` and added to `main.c`'s list of
+   commands (`cli_cmds[]`).  Commands should be specified with their name,
+   entrypoint and a brief description that can be printed in `git help`.
+   This is done because commands are linked into the main cli.
+
+3. Commands should accept a `--help` option that displays their help
+   information.  This will be shown when a user runs `<command> --help` and
+   when a user runs `help <command>`.
+
diff --git a/src/cli/cli.h b/src/cli/cli.h
new file mode 100644
index 0000000..7dede67
--- /dev/null
+++ b/src/cli/cli.h
@@ -0,0 +1,20 @@
+/*
+ * Copyright (C) the libgit2 contributors. All rights reserved.
+ *
+ * This file is part of libgit2, distributed under the GNU GPL v2 with
+ * a Linking Exception. For full terms see the included COPYING file.
+ */
+
+#ifndef CLI_cli_h__
+#define CLI_cli_h__
+
+#define PROGRAM_NAME "git2"
+
+#include "git2_util.h"
+
+#include "error.h"
+#include "opt.h"
+#include "opt_usage.h"
+#include "sighandler.h"
+
+#endif /* CLI_cli_h__ */
diff --git a/src/cli/cmd.c b/src/cli/cmd.c
new file mode 100644
index 0000000..2a7e71c
--- /dev/null
+++ b/src/cli/cmd.c
@@ -0,0 +1,21 @@
+/*
+ * Copyright (C) the libgit2 contributors. All rights reserved.
+ *
+ * This file is part of libgit2, distributed under the GNU GPL v2 with
+ * a Linking Exception. For full terms see the included COPYING file.
+ */
+
+#include "cli.h"
+#include "cmd.h"
+
+const cli_cmd_spec *cli_cmd_spec_byname(const char *name)
+{
+	const cli_cmd_spec *cmd;
+
+	for (cmd = cli_cmds; cmd->name; cmd++) {
+		if (!strcmp(cmd->name, name))
+			return cmd;
+	}
+
+	return NULL;
+}
diff --git a/src/cli/cmd.h b/src/cli/cmd.h
new file mode 100644
index 0000000..8b1a1b3
--- /dev/null
+++ b/src/cli/cmd.h
@@ -0,0 +1,33 @@
+/*
+ * Copyright (C) the libgit2 contributors. All rights reserved.
+ *
+ * This file is part of libgit2, distributed under the GNU GPL v2 with
+ * a Linking Exception. For full terms see the included COPYING file.
+ */
+
+#ifndef CLI_cmd_h__
+#define CLI_cmd_h__
+
+/* Command definitions */
+typedef struct {
+	const char *name;
+	int (*fn)(int argc, char **argv);
+	const char *desc;
+} cli_cmd_spec;
+
+/* Options that are common to all commands (eg --help, --git-dir) */
+extern const cli_opt_spec cli_common_opts[];
+
+/* All the commands supported by the CLI */
+extern const cli_cmd_spec cli_cmds[];
+
+/* Find a command by name */
+extern const cli_cmd_spec *cli_cmd_spec_byname(const char *name);
+
+/* Commands */
+extern int cmd_cat_file(int argc, char **argv);
+extern int cmd_clone(int argc, char **argv);
+extern int cmd_hash_object(int argc, char **argv);
+extern int cmd_help(int argc, char **argv);
+
+#endif /* CLI_cmd_h__ */
diff --git a/src/cli/cmd_cat_file.c b/src/cli/cmd_cat_file.c
new file mode 100644
index 0000000..fb53a72
--- /dev/null
+++ b/src/cli/cmd_cat_file.c
@@ -0,0 +1,204 @@
+/*
+ * Copyright (C) the libgit2 contributors. All rights reserved.
+ *
+ * This file is part of libgit2, distributed under the GNU GPL v2 with
+ * a Linking Exception. For full terms see the included COPYING file.
+ */
+
+#include <git2.h>
+#include "cli.h"
+#include "cmd.h"
+
+#define COMMAND_NAME "cat-file"
+
+typedef enum {
+	DISPLAY_CONTENT = 0,
+	DISPLAY_EXISTS,
+	DISPLAY_PRETTY,
+	DISPLAY_SIZE,
+	DISPLAY_TYPE
+} display_t;
+
+static int show_help;
+static int display = DISPLAY_CONTENT;
+static char *type_name, *object_spec;
+
+static const cli_opt_spec opts[] = {
+	{ CLI_OPT_TYPE_SWITCH,    "help",    0, &show_help,   1,
+	  CLI_OPT_USAGE_HIDDEN | CLI_OPT_USAGE_STOP_PARSING, NULL,
+	  "display help about the " COMMAND_NAME " command" },
+
+	{ CLI_OPT_TYPE_SWITCH,     NULL,    't', &display,    DISPLAY_TYPE,
+	  CLI_OPT_USAGE_REQUIRED,  NULL,    "display the type of the object" },
+	{ CLI_OPT_TYPE_SWITCH,     NULL,    's', &display,    DISPLAY_SIZE,
+	  CLI_OPT_USAGE_CHOICE,    NULL,    "display the size of the object" },
+	{ CLI_OPT_TYPE_SWITCH,     NULL,    'e', &display,    DISPLAY_EXISTS,
+	  CLI_OPT_USAGE_CHOICE,    NULL,    "displays nothing unless the object is corrupt" },
+	{ CLI_OPT_TYPE_SWITCH,     NULL,    'p', &display,    DISPLAY_PRETTY,
+	  CLI_OPT_USAGE_CHOICE,    NULL,    "pretty-print the object" },
+	{ CLI_OPT_TYPE_ARG,       "type",    0, &type_name,   0,
+	  CLI_OPT_USAGE_CHOICE,   "type",   "the type of object to display" },
+	{ CLI_OPT_TYPE_ARG,       "object",  0, &object_spec, 0,
+	  CLI_OPT_USAGE_REQUIRED, "object", "the object to display" },
+	{ 0 },
+};
+
+static void print_help(void)
+{
+	cli_opt_usage_fprint(stdout, PROGRAM_NAME, COMMAND_NAME, opts);
+	printf("\n");
+
+	printf("Display the content for the given object in the repository.\n");
+	printf("\n");
+
+	printf("Options:\n");
+
+	cli_opt_help_fprint(stdout, opts);
+}
+
+static int print_odb(git_object *object, display_t display)
+{
+	git_odb *odb = NULL;
+	git_odb_object *odb_object = NULL;
+	const unsigned char *content;
+	git_object_size_t size;
+	int ret = 0;
+
+	/*
+	 * Our parsed blobs retain the raw content; all other objects are
+	 * parsed into a working representation.  To get the raw content,
+	 * we need to do an ODB lookup.  (Thankfully, this should be cached
+	 * in-memory from our last call.)
+	 */
+	if (git_object_type(object) == GIT_OBJECT_BLOB) {
+		content = git_blob_rawcontent((git_blob *)object);
+		size = git_blob_rawsize((git_blob *)object);
+	} else {
+		if (git_repository_odb(&odb, git_object_owner(object)) < 0 ||
+		    git_odb_read(&odb_object, odb, git_object_id(object)) < 0) {
+			ret = cli_error_git();
+			goto done;
+		}
+
+		content = git_odb_object_data(odb_object);
+		size = git_odb_object_size(odb_object);
+	}
+
+	switch (display) {
+	case DISPLAY_SIZE:
+		if (printf("%" PRIu64 "\n", size) < 0)
+			ret = cli_error_os();
+		break;
+	case DISPLAY_CONTENT:
+		if (p_write(fileno(stdout), content, (size_t)size) < 0)
+			ret = cli_error_os();
+		break;
+	default:
+		GIT_ASSERT(0);
+	}
+
+done:
+	git_odb_object_free(odb_object);
+	git_odb_free(odb);
+	return ret;
+}
+
+static int print_type(git_object *object)
+{
+	if (printf("%s\n", git_object_type2string(git_object_type(object))) < 0)
+		return cli_error_os();
+
+	return 0;
+}
+
+static int print_pretty(git_object *object)
+{
+	const git_tree_entry *entry;
+	size_t i, count;
+
+	/*
+	 * Only trees are stored in an unreadable format and benefit from
+	 * pretty-printing.
+	 */
+	if (git_object_type(object) != GIT_OBJECT_TREE)
+		return print_odb(object, DISPLAY_CONTENT);
+
+	for (i = 0, count = git_tree_entrycount((git_tree *)object); i < count; i++) {
+		entry = git_tree_entry_byindex((git_tree *)object, i);
+
+		if (printf("%06o %s %s\t%s\n",
+		           git_tree_entry_filemode_raw(entry),
+		           git_object_type2string(git_tree_entry_type(entry)),
+		           git_oid_tostr_s(git_tree_entry_id(entry)),
+		           git_tree_entry_name(entry)) < 0)
+			return cli_error_os();
+	}
+
+	return 0;
+}
+
+int cmd_cat_file(int argc, char **argv)
+{
+	git_repository *repo = NULL;
+	git_object *object = NULL;
+	git_object_t type;
+	cli_opt invalid_opt;
+	int giterr, ret = 0;
+
+	if (cli_opt_parse(&invalid_opt, opts, argv + 1, argc - 1, CLI_OPT_PARSE_GNU))
+		return cli_opt_usage_error(COMMAND_NAME, opts, &invalid_opt);
+
+	if (show_help) {
+		print_help();
+		return 0;
+	}
+
+	if (git_repository_open_ext(&repo, ".", GIT_REPOSITORY_OPEN_FROM_ENV, NULL) < 0)
+		return cli_error_git();
+
+	if ((giterr = git_revparse_single(&object, repo, object_spec)) < 0) {
+		if (display == DISPLAY_EXISTS && giterr == GIT_ENOTFOUND)
+			ret = 1;
+		else
+			ret = cli_error_git();
+
+		goto done;
+	}
+
+	if (type_name) {
+		git_object *peeled;
+
+		if ((type = git_object_string2type(type_name)) == GIT_OBJECT_INVALID) {
+			ret = cli_error_usage("invalid object type '%s'", type_name);
+			goto done;
+		}
+
+		if (git_object_peel(&peeled, object, type) < 0) {
+			ret = cli_error_git();
+			goto done;
+		}
+
+		git_object_free(object);
+		object = peeled;
+	}
+
+	switch (display) {
+	case DISPLAY_EXISTS:
+		ret = 0;
+		break;
+	case DISPLAY_TYPE:
+		ret = print_type(object);
+		break;
+	case DISPLAY_PRETTY:
+		ret = print_pretty(object);
+		break;
+	default:
+		ret = print_odb(object, display);
+		break;
+	}
+
+done:
+	git_object_free(object);
+	git_repository_free(repo);
+	return ret;
+}
diff --git a/src/cli/cmd_clone.c b/src/cli/cmd_clone.c
new file mode 100644
index 0000000..e477625
--- /dev/null
+++ b/src/cli/cmd_clone.c
@@ -0,0 +1,192 @@
+/*
+ * Copyright (C) the libgit2 contributors. All rights reserved.
+ *
+ * This file is part of libgit2, distributed under the GNU GPL v2 with
+ * a Linking Exception. For full terms see the included COPYING file.
+ */
+
+#include <stdio.h>
+#include <git2.h>
+#include "cli.h"
+#include "cmd.h"
+#include "error.h"
+#include "sighandler.h"
+#include "progress.h"
+
+#include "fs_path.h"
+#include "futils.h"
+
+#define COMMAND_NAME "clone"
+
+static char *branch, *remote_path, *local_path, *depth;
+static int show_help, quiet, checkout = 1, bare;
+static bool local_path_exists;
+static cli_progress progress = CLI_PROGRESS_INIT;
+
+static const cli_opt_spec opts[] = {
+	{ CLI_OPT_TYPE_SWITCH,    "help",         0,  &show_help,   1,
+	  CLI_OPT_USAGE_HIDDEN | CLI_OPT_USAGE_STOP_PARSING, NULL,
+	  "display help about the " COMMAND_NAME " command" },
+
+	{ CLI_OPT_TYPE_SWITCH,    "quiet",       'q', &quiet,       1,
+	  CLI_OPT_USAGE_DEFAULT,   NULL,         "display the type of the object" },
+	{ CLI_OPT_TYPE_SWITCH,    "no-checkout", 'n', &checkout,    0,
+	  CLI_OPT_USAGE_DEFAULT,   NULL,         "don't checkout HEAD" },
+	{ CLI_OPT_TYPE_SWITCH,    "bare",         0,  &bare,        1,
+	  CLI_OPT_USAGE_DEFAULT,   NULL,         "don't create a working directory" },
+	{ CLI_OPT_TYPE_VALUE,     "branch",      'b', &branch,      0,
+	  CLI_OPT_USAGE_DEFAULT,  "name",        "branch to check out" },
+	{ CLI_OPT_TYPE_VALUE,     "depth",       0,   &depth,       0,
+	  CLI_OPT_USAGE_DEFAULT,  "depth",       "commit depth to check out " },
+	{ CLI_OPT_TYPE_LITERAL },
+	{ CLI_OPT_TYPE_ARG,       "repository",   0,  &remote_path, 0,
+	  CLI_OPT_USAGE_REQUIRED, "repository",  "repository path" },
+	{ CLI_OPT_TYPE_ARG,       "directory",    0,  &local_path,  0,
+	  CLI_OPT_USAGE_DEFAULT,  "directory",    "directory to clone into" },
+	{ 0 }
+};
+
+static void print_help(void)
+{
+	cli_opt_usage_fprint(stdout, PROGRAM_NAME, COMMAND_NAME, opts);
+	printf("\n");
+
+	printf("Clone a repository into a new directory.\n");
+	printf("\n");
+
+	printf("Options:\n");
+
+	cli_opt_help_fprint(stdout, opts);
+}
+
+static char *compute_local_path(const char *orig_path)
+{
+	const char *slash;
+	char *local_path;
+
+	if ((slash = strrchr(orig_path, '/')) == NULL &&
+	    (slash = strrchr(orig_path, '\\')) == NULL)
+		local_path = git__strdup(orig_path);
+	else
+		local_path = git__strdup(slash + 1);
+
+	return local_path;
+}
+
+static int compute_depth(const char *depth)
+{
+	int64_t i;
+	const char *endptr;
+
+	if (!depth)
+		return 0;
+
+	if (git__strntol64(&i, depth, strlen(depth), &endptr, 10) < 0 || i < 0 || i > INT_MAX || *endptr) {
+		fprintf(stderr, "fatal: depth '%s' is not valid.\n", depth);
+		exit(128);
+	}
+
+	return (int)i;
+}
+
+static bool validate_local_path(const char *path)
+{
+	if (!git_fs_path_exists(path))
+		return false;
+
+	if (!git_fs_path_isdir(path) || !git_fs_path_is_empty_dir(path)) {
+		fprintf(stderr, "fatal: destination path '%s' already exists and is not an empty directory.\n",
+			path);
+		exit(128);
+	}
+
+	return true;
+}
+
+static void cleanup(void)
+{
+	int rmdir_flags = GIT_RMDIR_REMOVE_FILES;
+
+	cli_progress_abort(&progress);
+
+	if (local_path_exists)
+		rmdir_flags |= GIT_RMDIR_SKIP_ROOT;
+
+	if (!git_fs_path_isdir(local_path))
+		return;
+
+	git_futils_rmdir_r(local_path, NULL, rmdir_flags);
+}
+
+static void interrupt_cleanup(void)
+{
+	cleanup();
+	exit(130);
+}
+
+int cmd_clone(int argc, char **argv)
+{
+	git_clone_options clone_opts = GIT_CLONE_OPTIONS_INIT;
+	git_repository *repo = NULL;
+	cli_opt invalid_opt;
+	char *computed_path = NULL;
+	int ret = 0;
+
+	if (cli_opt_parse(&invalid_opt, opts, argv + 1, argc - 1, CLI_OPT_PARSE_GNU))
+		return cli_opt_usage_error(COMMAND_NAME, opts, &invalid_opt);
+
+	if (show_help) {
+		print_help();
+		return 0;
+	}
+
+	if (!remote_path) {
+		ret = cli_error_usage("you must specify a repository to clone");
+		goto done;
+	}
+
+	clone_opts.bare = !!bare;
+	clone_opts.checkout_branch = branch;
+	clone_opts.fetch_opts.depth = compute_depth(depth);
+
+	if (!checkout)
+		clone_opts.checkout_opts.checkout_strategy = GIT_CHECKOUT_NONE;
+
+	if (!local_path)
+		local_path = computed_path = compute_local_path(remote_path);
+
+	local_path_exists = validate_local_path(local_path);
+
+	cli_sighandler_set_interrupt(interrupt_cleanup);
+
+	if (!local_path_exists &&
+	    git_futils_mkdir(local_path, 0777, 0) < 0) {
+		ret = cli_error_git();
+		goto done;
+	}
+
+	if (!quiet) {
+		clone_opts.fetch_opts.callbacks.sideband_progress = cli_progress_fetch_sideband;
+		clone_opts.fetch_opts.callbacks.transfer_progress = cli_progress_fetch_transfer;
+		clone_opts.fetch_opts.callbacks.payload = &progress;
+
+		clone_opts.checkout_opts.progress_cb = cli_progress_checkout;
+		clone_opts.checkout_opts.progress_payload = &progress;
+
+		printf("Cloning into '%s'...\n", local_path);
+	}
+
+	if (git_clone(&repo, remote_path, local_path, &clone_opts) < 0) {
+		cleanup();
+		ret = cli_error_git();
+		goto done;
+	}
+
+	cli_progress_finish(&progress);
+
+done:
+	cli_progress_dispose(&progress);
+	git__free(computed_path);
+	git_repository_free(repo);
+	return ret;
+}
diff --git a/src/cli/cmd_hash_object.c b/src/cli/cmd_hash_object.c
new file mode 100644
index 0000000..93b980d
--- /dev/null
+++ b/src/cli/cmd_hash_object.c
@@ -0,0 +1,154 @@
+/*
+ * Copyright (C) the libgit2 contributors. All rights reserved.
+ *
+ * This file is part of libgit2, distributed under the GNU GPL v2 with
+ * a Linking Exception. For full terms see the included COPYING file.
+ */
+
+#include <git2.h>
+#include "cli.h"
+#include "cmd.h"
+
+#include "futils.h"
+
+#define COMMAND_NAME "hash-object"
+
+static int show_help;
+static char *type_name;
+static int write_object, read_stdin, literally;
+static char **filenames;
+
+static const cli_opt_spec opts[] = {
+	{ CLI_OPT_TYPE_SWITCH,   "help",      0, &show_help,    1,
+	  CLI_OPT_USAGE_HIDDEN | CLI_OPT_USAGE_STOP_PARSING, NULL,
+	  "display help about the " COMMAND_NAME " command" },
+
+	{ CLI_OPT_TYPE_VALUE,     NULL,      't', &type_name,    0,
+	  CLI_OPT_USAGE_DEFAULT, "type",     "the type of object to hash (default: \"blob\")" },
+	{ CLI_OPT_TYPE_SWITCH,    NULL,      'w', &write_object, 1,
+	  CLI_OPT_USAGE_DEFAULT,  NULL,      "write the object to the object database" },
+	{ CLI_OPT_TYPE_SWITCH,   "literally", 0, &literally,    1,
+	  CLI_OPT_USAGE_DEFAULT,  NULL,      "do not validate the object contents" },
+	{ CLI_OPT_TYPE_SWITCH,   "stdin",     0, &read_stdin,   1,
+	  CLI_OPT_USAGE_REQUIRED, NULL,      "read content from stdin" },
+	{ CLI_OPT_TYPE_ARGS,     "file",      0, &filenames,    0,
+	  CLI_OPT_USAGE_CHOICE,  "file",     "the file (or files) to read and hash" },
+	{ 0 },
+};
+
+static void print_help(void)
+{
+	cli_opt_usage_fprint(stdout, PROGRAM_NAME, COMMAND_NAME, opts);
+	printf("\n");
+
+	printf("Compute the object ID for a given file and optionally write that file\nto the object database.\n");
+	printf("\n");
+
+	printf("Options:\n");
+
+	cli_opt_help_fprint(stdout, opts);
+}
+
+static int hash_buf(
+	git_odb *odb,
+	git_str *buf,
+	git_object_t object_type,
+	git_oid_t oid_type)
+{
+	git_oid oid;
+
+	if (!literally) {
+		int valid = 0;
+
+#ifdef GIT_EXPERIMENTAL_SHA256
+		if (git_object_rawcontent_is_valid(&valid, buf->ptr, buf->size, object_type, oid_type) < 0 || !valid)
+			return cli_error_git();
+#else
+		GIT_UNUSED(oid_type);
+
+		if (git_object_rawcontent_is_valid(&valid, buf->ptr, buf->size, object_type) < 0 || !valid)
+			return cli_error_git();
+#endif
+	}
+
+	if (write_object) {
+		if (git_odb_write(&oid, odb, buf->ptr, buf->size, object_type) < 0)
+			return cli_error_git();
+	} else {
+#ifdef GIT_EXPERIMENTAL_SHA256
+		if (git_odb_hash(&oid, buf->ptr, buf->size, object_type, GIT_OID_SHA1) < 0)
+			return cli_error_git();
+#else
+		if (git_odb_hash(&oid, buf->ptr, buf->size, object_type) < 0)
+			return cli_error_git();
+#endif
+	}
+
+	if (printf("%s\n", git_oid_tostr_s(&oid)) < 0)
+		return cli_error_os();
+
+	return 0;
+}
+
+int cmd_hash_object(int argc, char **argv)
+{
+	git_repository *repo = NULL;
+	git_odb *odb = NULL;
+	git_oid_t oid_type;
+	git_str buf = GIT_STR_INIT;
+	cli_opt invalid_opt;
+	git_object_t object_type = GIT_OBJECT_BLOB;
+	char **filename;
+	int ret = 0;
+
+	if (cli_opt_parse(&invalid_opt, opts, argv + 1, argc - 1, CLI_OPT_PARSE_GNU))
+		return cli_opt_usage_error(COMMAND_NAME, opts, &invalid_opt);
+
+	if (show_help) {
+		print_help();
+		return 0;
+	}
+
+	if (type_name && (object_type = git_object_string2type(type_name)) == GIT_OBJECT_INVALID)
+		return cli_error_usage("invalid object type '%s'", type_name);
+
+	if (write_object &&
+	    (git_repository_open_ext(&repo, ".", GIT_REPOSITORY_OPEN_FROM_ENV, NULL) < 0 ||
+	     git_repository_odb(&odb, repo) < 0)) {
+		ret = cli_error_git();
+		goto done;
+	}
+
+	oid_type = git_repository_oid_type(repo);
+
+	/*
+	 * TODO: we're reading blobs, we shouldn't pull them all into main
+	 * memory, we should just stream them into the odb instead.
+	 * (Or create a `git_odb_writefile` API.)
+	 */
+	if (read_stdin) {
+		if (git_futils_readbuffer_fd_full(&buf, fileno(stdin)) < 0) {
+			ret = cli_error_git();
+			goto done;
+		}
+
+		if ((ret = hash_buf(odb, &buf, object_type, oid_type)) != 0)
+			goto done;
+	} else {
+		for (filename = filenames; *filename; filename++) {
+			if (git_futils_readbuffer(&buf, *filename) < 0) {
+				ret = cli_error_git();
+				goto done;
+			}
+
+			if ((ret = hash_buf(odb, &buf, object_type, oid_type)) != 0)
+				goto done;
+		}
+	}
+
+done:
+	git_str_dispose(&buf);
+	git_odb_free(odb);
+	git_repository_free(repo);
+	return ret;
+}
diff --git a/src/cli/cmd_help.c b/src/cli/cmd_help.c
new file mode 100644
index 0000000..7ee9822
--- /dev/null
+++ b/src/cli/cmd_help.c
@@ -0,0 +1,86 @@
+/*
+ * Copyright (C) the libgit2 contributors. All rights reserved.
+ *
+ * This file is part of libgit2, distributed under the GNU GPL v2 with
+ * a Linking Exception. For full terms see the included COPYING file.
+ */
+
+#include <stdio.h>
+#include <git2.h>
+#include "cli.h"
+#include "cmd.h"
+
+#define COMMAND_NAME "help"
+
+static char *command;
+static int show_help;
+
+static const cli_opt_spec opts[] = {
+	{ CLI_OPT_TYPE_SWITCH,   "help",     0, &show_help, 1,
+	  CLI_OPT_USAGE_HIDDEN,   NULL,     "display help about the help command" },
+	{ CLI_OPT_TYPE_ARG,      "command",  0, &command,   0,
+	  CLI_OPT_USAGE_DEFAULT, "command", "the command to show help for" },
+	{ 0 },
+};
+
+static int print_help(void)
+{
+	cli_opt_usage_fprint(stdout, PROGRAM_NAME, COMMAND_NAME, opts);
+	printf("\n");
+
+	printf("Display help information about %s.  If a command is specified, help\n", PROGRAM_NAME);
+	printf("about that command will be shown.  Otherwise, general information about\n");
+	printf("%s will be shown, including the commands available.\n", PROGRAM_NAME);
+
+	return 0;
+}
+
+static int print_commands(void)
+{
+	const cli_cmd_spec *cmd;
+
+	cli_opt_usage_fprint(stdout, PROGRAM_NAME, NULL, cli_common_opts);
+	printf("\n");
+
+	printf("These are the %s commands available:\n\n", PROGRAM_NAME);
+
+	for (cmd = cli_cmds; cmd->name; cmd++)
+		printf("   %-11s  %s\n", cmd->name, cmd->desc);
+
+	printf("\nSee '%s help <command>' for more information on a specific command.\n", PROGRAM_NAME);
+
+	return 0;
+}
+
+int cmd_help(int argc, char **argv)
+{
+	char *fake_args[2];
+	const cli_cmd_spec *cmd;
+	cli_opt invalid_opt;
+
+	if (cli_opt_parse(&invalid_opt, opts, argv + 1, argc - 1, CLI_OPT_PARSE_GNU))
+		return cli_opt_usage_error(COMMAND_NAME, opts, &invalid_opt);
+
+	/* Show the meta-help */
+	if (show_help)
+		return print_help();
+
+	/* We were not asked to show help for a specific command. */
+	if (!command)
+		return print_commands();
+
+	/*
+	 * If we were asked for help for a command (eg, `help <command>`),
+	 * delegate back to that command's `--help` option.  This lets
+	 * commands own their help.  Emulate the command-line arguments
+	 * that would invoke `<command> --help` and invoke that command.
+	 */
+	fake_args[0] = command;
+	fake_args[1] = "--help";
+
+	if ((cmd = cli_cmd_spec_byname(command)) == NULL)
+		return cli_error("'%s' is not a %s command. See '%s help'.",
+		                command, PROGRAM_NAME, PROGRAM_NAME);
+
+	return cmd->fn(2, fake_args);
+}
diff --git a/src/cli/error.h b/src/cli/error.h
new file mode 100644
index 0000000..cce7a54
--- /dev/null
+++ b/src/cli/error.h
@@ -0,0 +1,51 @@
+/*
+ * Copyright (C) the libgit2 contributors. All rights reserved.
+ *
+ * This file is part of libgit2, distributed under the GNU GPL v2 with
+ * a Linking Exception. For full terms see the included COPYING file.
+ */
+
+#ifndef CLI_error_h__
+#define CLI_error_h__
+
+#include "cli.h"
+#include <stdio.h>
+
+#define CLI_EXIT_OK      0
+#define CLI_EXIT_ERROR   1
+#define CLI_EXIT_OS    128
+#define CLI_EXIT_GIT   128
+#define CLI_EXIT_USAGE 129
+
+#define cli_error__print(fmt) do { \
+		va_list ap; \
+		va_start(ap, fmt); \
+		fprintf(stderr, "%s: ", PROGRAM_NAME); \
+		vfprintf(stderr, fmt, ap); \
+		fprintf(stderr, "\n"); \
+		va_end(ap); \
+	} while(0)
+
+GIT_INLINE(int) cli_error(const char *fmt, ...)
+{
+	cli_error__print(fmt);
+	return CLI_EXIT_ERROR;
+}
+
+GIT_INLINE(int) cli_error_usage(const char *fmt, ...)
+{
+	cli_error__print(fmt);
+	return CLI_EXIT_USAGE;
+}
+
+GIT_INLINE(int) cli_error_git(void)
+{
+	const git_error *err = git_error_last();
+	fprintf(stderr, "%s: %s\n", PROGRAM_NAME,
+	        err ? err->message : "unknown error");
+	return CLI_EXIT_GIT;
+}
+
+#define cli_error_os() (perror(PROGRAM_NAME), CLI_EXIT_OS)
+
+#endif /* CLI_error_h__ */
diff --git a/src/cli/main.c b/src/cli/main.c
new file mode 100644
index 0000000..cbfc50e
--- /dev/null
+++ b/src/cli/main.c
@@ -0,0 +1,106 @@
+/*
+ * Copyright (C) the libgit2 contributors. All rights reserved.
+ *
+ * This file is part of libgit2, distributed under the GNU GPL v2 with
+ * a Linking Exception. For full terms see the included COPYING file.
+ */
+
+#include <stdio.h>
+#include <git2.h>
+#include "cli.h"
+#include "cmd.h"
+
+static int show_help = 0;
+static int show_version = 0;
+static char *command = NULL;
+static char **args = NULL;
+
+const cli_opt_spec cli_common_opts[] = {
+	{ CLI_OPT_TYPE_SWITCH,    "help",      0, &show_help,    1,
+	  CLI_OPT_USAGE_DEFAULT,   NULL,      "display help information" },
+	{ CLI_OPT_TYPE_SWITCH,    "version",   0, &show_version, 1,
+	  CLI_OPT_USAGE_DEFAULT,   NULL,      "display the version" },
+	{ CLI_OPT_TYPE_ARG,       "command",   0, &command,      0,
+	  CLI_OPT_USAGE_REQUIRED, "command", "the command to run" },
+	{ CLI_OPT_TYPE_ARGS,      "args",      0, &args,         0,
+	  CLI_OPT_USAGE_DEFAULT,  "args",    "arguments for the command" },
+	{ 0 }
+};
+
+const cli_cmd_spec cli_cmds[] = {
+	{ "cat-file",    cmd_cat_file,    "Display an object in the repository" },
+	{ "clone",       cmd_clone,       "Clone a repository into a new directory" },
+	{ "hash-object", cmd_hash_object, "Hash a raw object and product its object ID" },
+	{ "help",        cmd_help,        "Display help information" },
+	{ NULL }
+};
+
+int main(int argc, char **argv)
+{
+	const cli_cmd_spec *cmd;
+	cli_opt_parser optparser;
+	cli_opt opt;
+	char *help_args[3] = { NULL };
+	int help_args_len;
+	int args_len = 0;
+	int ret = 0;
+
+	if (git_libgit2_init() < 0) {
+		cli_error("failed to initialize libgit2");
+		exit(CLI_EXIT_GIT);
+	}
+
+	cli_opt_parser_init(&optparser, cli_common_opts, argv + 1, argc - 1, CLI_OPT_PARSE_GNU);
+
+	/* Parse the top-level (common) options and command information */
+	while (cli_opt_parser_next(&opt, &optparser)) {
+		if (!opt.spec) {
+			cli_opt_status_fprint(stderr, PROGRAM_NAME, &opt);
+			cli_opt_usage_fprint(stderr, PROGRAM_NAME, NULL, cli_common_opts);
+			ret = CLI_EXIT_USAGE;
+			goto done;
+		}
+
+		/*
+		 * When we see a command, stop parsing and capture the
+		 * remaining arguments as args for the command itself.
+		 */
+		if (command) {
+			args = &argv[optparser.idx];
+			args_len = (int)(argc - optparser.idx);
+			break;
+		}
+	}
+
+	if (show_version) {
+		printf("%s version %s\n", PROGRAM_NAME, LIBGIT2_VERSION);
+		goto done;
+	}
+
+	/*
+	 * If `--help <command>` is specified, delegate to that command's
+	 * `--help` option.  If no command is specified, run the `help`
+	 * command.  Do this by updating the args to emulate that behavior.
+	 */
+	if (!command || show_help) {
+		help_args[0] = command ? (char *)command : "help";
+		help_args[1] = command ? "--help" : NULL;
+		help_args_len = command ? 2 : 1;
+
+		command = help_args[0];
+		args = help_args;
+		args_len = help_args_len;
+	}
+
+	if ((cmd = cli_cmd_spec_byname(command)) == NULL) {
+		ret = cli_error("'%s' is not a %s command. See '%s help'.",
+		                command, PROGRAM_NAME, PROGRAM_NAME);
+		goto done;
+	}
+
+	ret = cmd->fn(args_len, args);
+
+done:
+	git_libgit2_shutdown();
+	return ret;
+}
diff --git a/src/cli/opt.c b/src/cli/opt.c
new file mode 100644
index 0000000..62a3430
--- /dev/null
+++ b/src/cli/opt.c
@@ -0,0 +1,669 @@
+/*
+ * Copyright (c), Edward Thomson <ethomson@edwardthomson.com>
+ * All rights reserved.
+ *
+ * This file is part of adopt, distributed under the MIT license.
+ * For full terms and conditions, see the included LICENSE file.
+ *
+ * THIS FILE IS AUTOMATICALLY GENERATED; DO NOT EDIT.
+ *
+ * This file was produced by using the `rename.pl` script included with
+ * adopt.  The command-line specified was:
+ *
+ * ./rename.pl cli_opt --filename=opt --include=cli.h --inline=GIT_INLINE --header-guard=CLI_opt_h__ --lowercase-status --without-usage
+ */
+
+#include <stdlib.h>
+#include <string.h>
+#include <stdio.h>
+#include <limits.h>
+#include <assert.h>
+
+#include "cli.h"
+#include "opt.h"
+
+#ifdef _WIN32
+# include <windows.h>
+#else
+# include <fcntl.h>
+# include <sys/ioctl.h>
+#endif
+
+#ifdef _MSC_VER
+# define alloca _alloca
+#endif
+
+#define spec_is_option_type(x) \
+	((x)->type == CLI_OPT_TYPE_BOOL || \
+	 (x)->type == CLI_OPT_TYPE_SWITCH || \
+	 (x)->type == CLI_OPT_TYPE_VALUE)
+
+GIT_INLINE(const cli_opt_spec *) spec_for_long(
+	int *is_negated,
+	int *has_value,
+	const char **value,
+	const cli_opt_parser *parser,
+	const char *arg)
+{
+	const cli_opt_spec *spec;
+	char *eql;
+	size_t eql_pos;
+
+	eql = strchr(arg, '=');
+	eql_pos = (eql = strchr(arg, '=')) ? (size_t)(eql - arg) : strlen(arg);
+
+	for (spec = parser->specs; spec->type; ++spec) {
+		/* Handle -- (everything after this is literal) */
+		if (spec->type == CLI_OPT_TYPE_LITERAL && arg[0] == '\0')
+			return spec;
+
+		/* Handle --no-option arguments for bool types */
+		if (spec->type == CLI_OPT_TYPE_BOOL &&
+		    strncmp(arg, "no-", 3) == 0 &&
+		    strcmp(arg + 3, spec->name) == 0) {
+			*is_negated = 1;
+			return spec;
+		}
+
+		/* Handle the typical --option arguments */
+		if (spec_is_option_type(spec) &&
+		    spec->name &&
+		    strcmp(arg, spec->name) == 0)
+			return spec;
+
+		/* Handle --option=value arguments */
+		if (spec->type == CLI_OPT_TYPE_VALUE &&
+		    eql &&
+		    strncmp(arg, spec->name, eql_pos) == 0 &&
+		    spec->name[eql_pos] == '\0') {
+			*has_value = 1;
+			*value = arg[eql_pos + 1] ? &arg[eql_pos + 1] : NULL;
+			return spec;
+		}
+	}
+
+	return NULL;
+}
+
+GIT_INLINE(const cli_opt_spec *) spec_for_short(
+	const char **value,
+	const cli_opt_parser *parser,
+	const char *arg)
+{
+	const cli_opt_spec *spec;
+
+	for (spec = parser->specs; spec->type; ++spec) {
+		/* Handle -svalue short options with a value */
+		if (spec->type == CLI_OPT_TYPE_VALUE &&
+		    arg[0] == spec->alias &&
+		    arg[1] != '\0') {
+			*value = &arg[1];
+			return spec;
+		}
+
+		/* Handle typical -s short options */
+		if (arg[0] == spec->alias) {
+			*value = NULL;
+			return spec;
+		}
+	}
+
+	return NULL;
+}
+
+GIT_INLINE(const cli_opt_spec *) spec_for_arg(cli_opt_parser *parser)
+{
+	const cli_opt_spec *spec;
+	size_t args = 0;
+
+	for (spec = parser->specs; spec->type; ++spec) {
+		if (spec->type == CLI_OPT_TYPE_ARG) {
+			if (args == parser->arg_idx) {
+				parser->arg_idx++;
+				return spec;
+			}
+
+			args++;
+		}
+
+		if (spec->type == CLI_OPT_TYPE_ARGS && args == parser->arg_idx)
+			return spec;
+	}
+
+	return NULL;
+}
+
+GIT_INLINE(int) spec_is_choice(const cli_opt_spec *spec)
+{
+	return ((spec + 1)->type &&
+	       ((spec + 1)->usage & CLI_OPT_USAGE_CHOICE));
+}
+
+/*
+ * If we have a choice with switches and bare arguments, and we see
+ * the switch, then we no longer expect the bare argument.
+ */
+GIT_INLINE(void) consume_choices(const cli_opt_spec *spec, cli_opt_parser *parser)
+{
+	/* back up to the beginning of the choices */
+	while (spec->type && (spec->usage & CLI_OPT_USAGE_CHOICE))
+		--spec;
+
+	if (!spec_is_choice(spec))
+		return;
+
+	do {
+		if (spec->type == CLI_OPT_TYPE_ARG)
+			parser->arg_idx++;
+		++spec;
+	} while(spec->type && (spec->usage & CLI_OPT_USAGE_CHOICE));
+}
+
+static cli_opt_status_t parse_long(cli_opt *opt, cli_opt_parser *parser)
+{
+	const cli_opt_spec *spec;
+	char *arg = parser->args[parser->idx++];
+	const char *value = NULL;
+	int is_negated = 0, has_value = 0;
+
+	opt->arg = arg;
+
+	if ((spec = spec_for_long(&is_negated, &has_value, &value, parser, &arg[2])) == NULL) {
+		opt->spec = NULL;
+		opt->status = CLI_OPT_STATUS_UNKNOWN_OPTION;
+		goto done;
+	}
+
+	opt->spec = spec;
+
+	/* Future options parsed as literal */
+	if (spec->type == CLI_OPT_TYPE_LITERAL)
+		parser->in_literal = 1;
+
+	/* --bool or --no-bool */
+	else if (spec->type == CLI_OPT_TYPE_BOOL && spec->value)
+		*((int *)spec->value) = !is_negated;
+
+	/* --accumulate */
+	else if (spec->type == CLI_OPT_TYPE_ACCUMULATOR && spec->value)
+		*((int *)spec->value) += spec->switch_value ? spec->switch_value : 1;
+
+	/* --switch */
+	else if (spec->type == CLI_OPT_TYPE_SWITCH && spec->value)
+		*((int *)spec->value) = spec->switch_value;
+
+	/* Parse values as "--foo=bar" or "--foo bar" */
+	else if (spec->type == CLI_OPT_TYPE_VALUE) {
+		if (has_value)
+			opt->value = (char *)value;
+		else if ((parser->idx + 1) <= parser->args_len)
+			opt->value = parser->args[parser->idx++];
+
+		if (spec->value)
+			*((char **)spec->value) = opt->value;
+	}
+
+	/* Required argument was not provided */
+	if (spec->type == CLI_OPT_TYPE_VALUE &&
+	    !opt->value &&
+	    !(spec->usage & CLI_OPT_USAGE_VALUE_OPTIONAL))
+		opt->status = CLI_OPT_STATUS_MISSING_VALUE;
+	else
+		opt->status = CLI_OPT_STATUS_OK;
+
+	consume_choices(opt->spec, parser);
+
+done:
+	return opt->status;
+}
+
+static cli_opt_status_t parse_short(cli_opt *opt, cli_opt_parser *parser)
+{
+	const cli_opt_spec *spec;
+	char *arg = parser->args[parser->idx++];
+	const char *value;
+
+	opt->arg = arg;
+
+	if ((spec = spec_for_short(&value, parser, &arg[1 + parser->in_short])) == NULL) {
+		opt->spec = NULL;
+		opt->status = CLI_OPT_STATUS_UNKNOWN_OPTION;
+		goto done;
+	}
+
+	opt->spec = spec;
+
+	if (spec->type == CLI_OPT_TYPE_BOOL && spec->value)
+		*((int *)spec->value) = 1;
+
+	else if (spec->type == CLI_OPT_TYPE_ACCUMULATOR && spec->value)
+		*((int *)spec->value) += spec->switch_value ? spec->switch_value : 1;
+
+	else if (spec->type == CLI_OPT_TYPE_SWITCH && spec->value)
+		*((int *)spec->value) = spec->switch_value;
+
+	/* Parse values as "-ifoo" or "-i foo" */
+	else if (spec->type == CLI_OPT_TYPE_VALUE) {
+		if (value)
+			opt->value = (char *)value;
+		else if ((parser->idx + 1) <= parser->args_len)
+			opt->value = parser->args[parser->idx++];
+
+		if (spec->value)
+			*((char **)spec->value) = opt->value;
+	}
+
+	/*
+	 * Handle compressed short arguments, like "-fbcd"; see if there's
+	 * another character after the one we processed.  If not, advance
+	 * the parser index.
+	 */
+	if (spec->type != CLI_OPT_TYPE_VALUE && arg[2 + parser->in_short] != '\0') {
+		parser->in_short++;
+		parser->idx--;
+	} else {
+		parser->in_short = 0;
+	}
+
+	/* Required argument was not provided */
+	if (spec->type == CLI_OPT_TYPE_VALUE && !opt->value)
+		opt->status = CLI_OPT_STATUS_MISSING_VALUE;
+	else
+		opt->status = CLI_OPT_STATUS_OK;
+
+	consume_choices(opt->spec, parser);
+
+done:
+	return opt->status;
+}
+
+static cli_opt_status_t parse_arg(cli_opt *opt, cli_opt_parser *parser)
+{
+	const cli_opt_spec *spec = spec_for_arg(parser);
+
+	opt->spec = spec;
+	opt->arg = parser->args[parser->idx];
+
+	if (!spec) {
+		parser->idx++;
+		opt->status = CLI_OPT_STATUS_UNKNOWN_OPTION;
+	} else if (spec->type == CLI_OPT_TYPE_ARGS) {
+		if (spec->value)
+			*((char ***)spec->value) = &parser->args[parser->idx];
+
+		/*
+		 * We have started a list of arguments; the remainder of
+		 * given arguments need not be examined.
+		 */
+		parser->in_args = (parser->args_len - parser->idx);
+		parser->idx = parser->args_len;
+		opt->args_len = parser->in_args;
+		opt->status = CLI_OPT_STATUS_OK;
+	} else {
+		if (spec->value)
+			*((char **)spec->value) = parser->args[parser->idx];
+
+		parser->idx++;
+		opt->status = CLI_OPT_STATUS_OK;
+	}
+
+	return opt->status;
+}
+
+static int support_gnu_style(unsigned int flags)
+{
+	if ((flags & CLI_OPT_PARSE_FORCE_GNU) != 0)
+		return 1;
+
+	if ((flags & CLI_OPT_PARSE_GNU) == 0)
+		return 0;
+
+	/* TODO: Windows */
+#if defined(_WIN32) && defined(UNICODE)
+	if (_wgetenv(L"POSIXLY_CORRECT") != NULL)
+		return 0;
+#else
+	if (getenv("POSIXLY_CORRECT") != NULL)
+		return 0;
+#endif
+
+	return 1;
+}
+
+void cli_opt_parser_init(
+	cli_opt_parser *parser,
+	const cli_opt_spec specs[],
+	char **args,
+	size_t args_len,
+	unsigned int flags)
+{
+	assert(parser);
+
+	memset(parser, 0x0, sizeof(cli_opt_parser));
+
+	parser->specs = specs;
+	parser->args = args;
+	parser->args_len = args_len;
+	parser->flags = flags;
+
+	parser->needs_sort = support_gnu_style(flags);
+}
+
+GIT_INLINE(const cli_opt_spec *) spec_for_sort(
+	int *needs_value,
+	const cli_opt_parser *parser,
+	const char *arg)
+{
+	int is_negated, has_value = 0;
+	const char *value;
+	const cli_opt_spec *spec = NULL;
+	size_t idx = 0;
+
+	*needs_value = 0;
+
+	if (strncmp(arg, "--", 2) == 0) {
+		spec = spec_for_long(&is_negated, &has_value, &value, parser, &arg[2]);
+		*needs_value = !has_value;
+	}
+
+	else if (strncmp(arg, "-", 1) == 0) {
+		spec = spec_for_short(&value, parser, &arg[1]);
+
+		/*
+		 * Advance through compressed short arguments to see if
+		 * the last one has a value, eg "-xvffilename".
+		 */
+		while (spec && !value && arg[1 + ++idx] != '\0')
+			spec = spec_for_short(&value, parser, &arg[1 + idx]);
+
+		*needs_value = (value == NULL);
+	}
+
+	return spec;
+}
+
+/*
+ * Some parsers allow for handling arguments like "file1 --help file2";
+ * this is done by re-sorting the arguments in-place; emulate that.
+ */
+static int sort_gnu_style(cli_opt_parser *parser)
+{
+	size_t i, j, insert_idx = parser->idx, offset;
+	const cli_opt_spec *spec;
+	char *option, *value;
+	int needs_value, changed = 0;
+
+	parser->needs_sort = 0;
+
+	for (i = parser->idx; i < parser->args_len; i++) {
+		spec = spec_for_sort(&needs_value, parser, parser->args[i]);
+
+		/* Not a "-" or "--" prefixed option.  No change. */
+		if (!spec)
+			continue;
+
+		/* A "--" alone means remaining args are literal. */
+		if (spec->type == CLI_OPT_TYPE_LITERAL)
+			break;
+
+		option = parser->args[i];
+
+		/*
+		 * If the argument is a value type and doesn't already
+		 * have a value (eg "--foo=bar" or "-fbar") then we need
+		 * to copy the next argument as its value.
+		 */
+		if (spec->type == CLI_OPT_TYPE_VALUE && needs_value) {
+			/*
+			 * A required value is not provided; set parser
+			 * index to this value so that we fail on it.
+			 */
+			if (i + 1 >= parser->args_len) {
+				parser->idx = i;
+				return 1;
+			}
+
+			value = parser->args[i + 1];
+			offset = 1;
+		} else {
+			value = NULL;
+			offset = 0;
+		}
+
+		/* Caller error if args[0] is an option. */
+		if (i == 0)
+			return 0;
+
+		/* Shift args up one (or two) and insert the option */
+		for (j = i; j > insert_idx; j--)
+			parser->args[j + offset] = parser->args[j - 1];
+
+		parser->args[insert_idx] = option;
+
+		if (value)
+			parser->args[insert_idx + 1] = value;
+
+		insert_idx += (1 + offset);
+		i += offset;
+
+		changed = 1;
+	}
+
+	return changed;
+}
+
+cli_opt_status_t cli_opt_parser_next(cli_opt *opt, cli_opt_parser *parser)
+{
+	assert(opt && parser);
+
+	memset(opt, 0x0, sizeof(cli_opt));
+
+	if (parser->idx >= parser->args_len) {
+		opt->args_len = parser->in_args;
+		return CLI_OPT_STATUS_DONE;
+	}
+
+	/* Handle options in long form, those beginning with "--" */
+	if (strncmp(parser->args[parser->idx], "--", 2) == 0 &&
+	    !parser->in_short &&
+	    !parser->in_literal)
+		return parse_long(opt, parser);
+
+	/* Handle options in short form, those beginning with "-" */
+	else if (parser->in_short ||
+	         (strncmp(parser->args[parser->idx], "-", 1) == 0 &&
+		  !parser->in_literal))
+		return parse_short(opt, parser);
+
+	/*
+	 * We've reached the first "bare" argument.  In POSIX mode, all
+	 * remaining items on the command line are arguments.  In GNU
+	 * mode, there may be long or short options after this.  Sort any
+	 * options up to this position then re-parse the current position.
+	 */
+	if (parser->needs_sort && sort_gnu_style(parser))
+		return cli_opt_parser_next(opt, parser);
+
+	return parse_arg(opt, parser);
+}
+
+GIT_INLINE(int) spec_included(const cli_opt_spec **specs, const cli_opt_spec *spec)
+{
+	const cli_opt_spec **i;
+
+	for (i = specs; *i; ++i) {
+		if (spec == *i)
+			return 1;
+	}
+
+	return 0;
+}
+
+static cli_opt_status_t validate_required(
+	cli_opt *opt,
+	const cli_opt_spec specs[],
+	const cli_opt_spec **given_specs)
+{
+	const cli_opt_spec *spec, *required;
+	int given;
+
+	/*
+	 * Iterate over the possible specs to identify requirements and
+	 * ensure that those have been given on the command-line.
+	 * Note that we can have required *choices*, where one in a
+	 * list of choices must be specified.
+	 */
+	for (spec = specs, required = NULL, given = 0; spec->type; ++spec) {
+		if (!required && (spec->usage & CLI_OPT_USAGE_REQUIRED)) {
+			required = spec;
+			given = 0;
+		} else if (!required) {
+			continue;
+		}
+
+		if (!given)
+			given = spec_included(given_specs, spec);
+
+		/*
+		 * Validate the requirement unless we're in a required
+		 * choice.  In that case, keep the required state and
+		 * validate at the end of the choice list.
+		 */
+		if (!spec_is_choice(spec)) {
+			if (!given) {
+				opt->spec = required;
+				opt->status = CLI_OPT_STATUS_MISSING_ARGUMENT;
+				break;
+			}
+
+			required = NULL;
+			given = 0;
+		}
+	}
+
+	return opt->status;
+}
+
+cli_opt_status_t cli_opt_parse(
+	cli_opt *opt,
+	const cli_opt_spec specs[],
+	char **args,
+	size_t args_len,
+	unsigned int flags)
+{
+	cli_opt_parser parser;
+	const cli_opt_spec **given_specs;
+	size_t given_idx = 0;
+
+	cli_opt_parser_init(&parser, specs, args, args_len, flags);
+
+	given_specs = alloca(sizeof(const cli_opt_spec *) * (args_len + 1));
+
+	while (cli_opt_parser_next(opt, &parser)) {
+		if (opt->status != CLI_OPT_STATUS_OK &&
+		    opt->status != CLI_OPT_STATUS_DONE)
+			return opt->status;
+
+		if ((opt->spec->usage & CLI_OPT_USAGE_STOP_PARSING))
+			return (opt->status = CLI_OPT_STATUS_DONE);
+
+		given_specs[given_idx++] = opt->spec;
+	}
+
+	given_specs[given_idx] = NULL;
+
+	return validate_required(opt, specs, given_specs);
+}
+
+static int spec_name_fprint(FILE *file, const cli_opt_spec *spec)
+{
+	int error;
+
+	if (spec->type == CLI_OPT_TYPE_ARG)
+		error = fprintf(file, "%s", spec->value_name);
+	else if (spec->type == CLI_OPT_TYPE_ARGS)
+		error = fprintf(file, "%s", spec->value_name);
+	else if (spec->alias && !(spec->usage & CLI_OPT_USAGE_SHOW_LONG))
+		error = fprintf(file, "-%c", spec->alias);
+	else
+		error = fprintf(file, "--%s", spec->name);
+
+	return error;
+}
+
+int cli_opt_status_fprint(
+	FILE *file,
+	const char *command,
+	const cli_opt *opt)
+{
+	const cli_opt_spec *choice;
+	int error;
+
+	if (command && (error = fprintf(file, "%s: ", command)) < 0)
+		return error;
+
+	switch (opt->status) {
+	case CLI_OPT_STATUS_DONE:
+		error = fprintf(file, "finished processing arguments (no error)\n");
+		break;
+	case CLI_OPT_STATUS_OK:
+		error = fprintf(file, "no error\n");
+		break;
+	case CLI_OPT_STATUS_UNKNOWN_OPTION:
+		error = fprintf(file, "unknown option: %s\n", opt->arg);
+		break;
+	case CLI_OPT_STATUS_MISSING_VALUE:
+		if ((error = fprintf(file, "argument '")) < 0 ||
+		    (error = spec_name_fprint(file, opt->spec)) < 0 ||
+		    (error = fprintf(file, "' requires a value.\n")) < 0)
+			break;
+		break;
+	case CLI_OPT_STATUS_MISSING_ARGUMENT:
+		if (spec_is_choice(opt->spec)) {
+			int is_choice = 1;
+
+			if (spec_is_choice((opt->spec)+1))
+				error = fprintf(file, "one of");
+			else
+				error = fprintf(file, "either");
+
+			if (error < 0)
+				break;
+
+			for (choice = opt->spec; is_choice; ++choice) {
+				is_choice = spec_is_choice(choice);
+
+				if (!is_choice)
+					error = fprintf(file, " or");
+				else if (choice != opt->spec)
+					error = fprintf(file, ",");
+
+				if ((error < 0) ||
+				    (error = fprintf(file, " '")) < 0 ||
+				    (error = spec_name_fprint(file, choice)) < 0 ||
+				    (error = fprintf(file, "'")) < 0)
+					break;
+
+				if (!spec_is_choice(choice))
+					break;
+			}
+
+			if ((error < 0) ||
+			    (error = fprintf(file, " is required.\n")) < 0)
+				break;
+		} else {
+			if ((error = fprintf(file, "argument '")) < 0 ||
+			    (error = spec_name_fprint(file, opt->spec)) < 0 ||
+			    (error = fprintf(file, "' is required.\n")) < 0)
+				break;
+		}
+
+		break;
+	default:
+		error = fprintf(file, "unknown status: %d\n", opt->status);
+		break;
+	}
+
+	return error;
+}
+
diff --git a/src/cli/opt.h b/src/cli/opt.h
new file mode 100644
index 0000000..6c1d460
--- /dev/null
+++ b/src/cli/opt.h
@@ -0,0 +1,349 @@
+/*
+ * Copyright (c), Edward Thomson <ethomson@edwardthomson.com>
+ * All rights reserved.
+ *
+ * This file is part of adopt, distributed under the MIT license.
+ * For full terms and conditions, see the included LICENSE file.
+ *
+ * THIS FILE IS AUTOMATICALLY GENERATED; DO NOT EDIT.
+ *
+ * This file was produced by using the `rename.pl` script included with
+ * adopt.  The command-line specified was:
+ *
+ * ./rename.pl cli_opt --filename=opt --include=cli.h --inline=GIT_INLINE --header-guard=CLI_opt_h__ --lowercase-status --without-usage
+ */
+
+#ifndef CLI_opt_h__
+#define CLI_opt_h__
+
+#include <stdio.h>
+#include <stdint.h>
+
+/**
+ * The type of argument to be parsed.
+ */
+typedef enum {
+	CLI_OPT_TYPE_NONE = 0,
+
+	/**
+	 * An option that, when specified, sets a given value to true.
+	 * This is useful for options like "--debug".  A negation
+	 * option (beginning with "no-") is implicitly specified; for
+	 * example "--no-debug".  The `value` pointer in the returned
+	 * option will be set to `1` when this is specified, and set to
+	 * `0` when the negation "no-" option is specified.
+	 */
+	CLI_OPT_TYPE_BOOL,
+
+	/**
+	 * An option that, when specified, sets the given `value` pointer
+	 * to the specified `switch_value`.  This is useful for booleans
+	 * where you do not want the implicit negation that comes with an
+	 * `CLI_OPT_TYPE_BOOL`, or for switches that multiplex a value, like
+	 * setting a mode.  For example, `--read` may set the `value` to
+	 * `MODE_READ` and `--write` may set the `value` to `MODE_WRITE`.
+	 */
+	CLI_OPT_TYPE_SWITCH,
+
+	/**
+	 * An option that, when specified, increments the given
+	 * `value` by the given `switch_value`.  This can be specified
+	 * multiple times to continue to increment the `value`.
+	 * (For example, "-vvv" to set verbosity to 3.)
+	 */
+	CLI_OPT_TYPE_ACCUMULATOR,
+
+	/**
+	 * An option that takes a value, for example `-n value`,
+	 * `-nvalue`, `--name value` or `--name=value`.
+	 */
+	CLI_OPT_TYPE_VALUE,
+
+	/**
+	 * A bare "--" that indicates that arguments following this are
+	 * literal.  This allows callers to specify things that might
+	 * otherwise look like options, for example to operate on a file
+	 * named "-rf" then you can invoke "program -- -rf" to treat
+	 * "-rf" as an argument not an option.
+	 */
+	CLI_OPT_TYPE_LITERAL,
+
+	/**
+	 * A single argument, not an option.  When options are exhausted,
+	 * arguments will be matches in the order that they're specified
+	 * in the spec list.  For example, if two `CLI_OPT_TYPE_ARGS` are
+	 * specified, `input_file` and `output_file`, then the first bare
+	 * argument on the command line will be `input_file` and the
+	 * second will be `output_file`.
+	 */
+	CLI_OPT_TYPE_ARG,
+
+	/**
+	 * A collection of arguments.  This is useful when you want to take
+	 * a list of arguments, for example, multiple paths.  When specified,
+	 * the value will be set to the first argument in the list.
+	 */
+	CLI_OPT_TYPE_ARGS,
+} cli_opt_type_t;
+
+/**
+ * Additional information about an option, including parsing
+ * restrictions and usage information to be displayed to the end-user.
+ */
+typedef enum {
+	/** Defaults for the argument. */
+	CLI_OPT_USAGE_DEFAULT  = 0,
+
+	/** This argument is required. */
+	CLI_OPT_USAGE_REQUIRED = (1u << 0),
+
+	/**
+	 * This is a multiple choice argument, combined with the previous
+	 * argument.  For example, when the previous argument is `-f` and
+	 * this optional is applied to an argument of type `-b` then one
+	 * of `-f` or `-b` may be specified.
+	 */
+	CLI_OPT_USAGE_CHOICE = (1u << 1),
+
+	/**
+	 * This argument short-circuits the remainder of parsing.
+	 * Useful for arguments like `--help`.
+	 */
+	CLI_OPT_USAGE_STOP_PARSING = (1u << 2),
+
+	/** The argument's value is optional ("-n" or "-n foo") */
+	CLI_OPT_USAGE_VALUE_OPTIONAL = (1u << 3),
+
+	/** This argument should not be displayed in usage. */
+	CLI_OPT_USAGE_HIDDEN = (1u << 4),
+
+	/** In usage, show the long format instead of the abbreviated format. */
+	CLI_OPT_USAGE_SHOW_LONG = (1u << 5),
+} cli_opt_usage_t;
+
+typedef enum {
+	/** Default parsing behavior. */
+	CLI_OPT_PARSE_DEFAULT  = 0,
+
+	/**
+	 * Parse with GNU `getopt_long` style behavior, where options can
+	 * be intermixed with arguments at any position (for example,
+	 * "file1 --help file2".)  Like `getopt_long`, this can mutate the
+	 * arguments given.
+	 */
+	CLI_OPT_PARSE_GNU = (1u << 0),
+
+	/**
+	 * Force GNU `getopt_long` style behavior; the `POSIXLY_CORRECT`
+	 * environment variable is ignored.
+	 */
+	CLI_OPT_PARSE_FORCE_GNU = (1u << 1),
+} cli_opt_flag_t;
+
+/** Specification for an available option. */
+typedef struct cli_opt_spec {
+	/** Type of option expected. */
+	cli_opt_type_t type;
+
+	/** Name of the long option. */
+	const char *name;
+
+	/** The alias is the short (one-character) option alias. */
+	const char alias;
+
+	/**
+	 * If this spec is of type `CLI_OPT_TYPE_BOOL`, this is a pointer
+	 * to an `int` that will be set to `1` if the option is specified.
+	 *
+	 * If this spec is of type `CLI_OPT_TYPE_SWITCH`, this is a pointer
+	 * to an `int` that will be set to the opt's `switch_value` (below)
+	 * when this option is specified.
+	 *
+	 * If this spec is of type `CLI_OPT_TYPE_ACCUMULATOR`, this is a
+	 * pointer to an `int` that will be incremented by the opt's
+	 * `switch_value` (below).  If no `switch_value` is provided then
+	 * the value will be incremented by 1.
+	 *
+	 * If this spec is of type `CLI_OPT_TYPE_VALUE`,
+	 * `CLI_OPT_TYPE_VALUE_OPTIONAL`, or `CLI_OPT_TYPE_ARG`, this is
+	 * a pointer to a `char *` that will be set to the value
+	 * specified on the command line.
+	 *
+	 * If this spec is of type `CLI_OPT_TYPE_ARGS`, this is a pointer
+	 * to a `char **` that will be set to the remaining values
+	 * specified on the command line.
+	 */
+	void *value;
+
+	/**
+	 * If this spec is of type `CLI_OPT_TYPE_SWITCH`, this is the value
+	 * to set in the option's `value` pointer when it is specified.  If
+	 * this spec is of type `CLI_OPT_TYPE_ACCUMULATOR`, this is the value
+	 * to increment in the option's `value` pointer when it is
+	 * specified.  This is ignored for other opt types.
+	 */
+	int switch_value;
+
+	/**
+	 * Optional usage flags that change parsing behavior and how
+	 * usage information is shown to the end-user.
+	 */
+	uint32_t usage;
+
+	/**
+	 * The name of the value, provided when creating usage information.
+	 * This is required only for the functions that display usage
+	 * information and only when a spec is of type `CLI_OPT_TYPE_VALUE,
+	 * `CLI_OPT_TYPE_ARG` or `CLI_OPT_TYPE_ARGS``.
+	 */
+	const char *value_name;
+
+	/**
+	 * Optional short description of the option to display to the
+	 * end-user.  This is only used when creating usage information.
+	 */
+	const char *help;
+} cli_opt_spec;
+
+/** Return value for `cli_opt_parser_next`. */
+typedef enum {
+	/** Parsing is complete; there are no more arguments. */
+	CLI_OPT_STATUS_DONE = 0,
+
+	/**
+	 * This argument was parsed correctly; the `opt` structure is
+	 * populated and the value pointer has been set.
+	 */
+	CLI_OPT_STATUS_OK = 1,
+
+	/**
+	 * The argument could not be parsed correctly, it does not match
+	 * any of the specifications provided.
+	 */
+	CLI_OPT_STATUS_UNKNOWN_OPTION = 2,
+
+	/**
+	 * The argument matched a spec of type `CLI_OPT_VALUE`, but no value
+	 * was provided.
+	 */
+	CLI_OPT_STATUS_MISSING_VALUE = 3,
+
+	/** A required argument was not provided. */
+	CLI_OPT_STATUS_MISSING_ARGUMENT = 4,
+} cli_opt_status_t;
+
+/** An option provided on the command-line. */
+typedef struct cli_opt {
+	/** The status of parsing the most recent argument. */
+	cli_opt_status_t status;
+
+	/**
+	 * The specification that was provided on the command-line, or
+	 * `NULL` if the argument did not match an `cli_opt_spec`.
+	 */
+	const cli_opt_spec *spec;
+
+	/**
+	 * The argument as it was specified on the command-line, including
+	 * dashes, eg, `-f` or `--foo`.
+	 */
+	char *arg;
+
+	/**
+	 * If the spec is of type `CLI_OPT_VALUE` or `CLI_OPT_VALUE_OPTIONAL`,
+	 * this is the value provided to the argument.
+	 */
+	char *value;
+
+	/**
+	 * If the argument is of type `CLI_OPT_ARGS`, this is the number of
+	 * arguments remaining.  This value is persisted even when parsing
+	 * is complete and `status` == `CLI_OPT_STATUS_DONE`.
+	 */
+	size_t args_len;
+} cli_opt;
+
+/* The internal parser state.  Callers should not modify this structure. */
+typedef struct cli_opt_parser {
+	const cli_opt_spec *specs;
+	char **args;
+	size_t args_len;
+	unsigned int flags;
+
+	/* Parser state */
+	size_t idx;
+	size_t arg_idx;
+	size_t in_args;
+	size_t in_short;
+	int needs_sort : 1,
+	    in_literal : 1;
+} cli_opt_parser;
+
+/**
+ * Parses all the command-line arguments and updates all the options using
+ * the pointers provided.  Parsing stops on any invalid argument and
+ * information about the failure will be provided in the opt argument.
+ *
+ * This is the simplest way to parse options; it handles the initialization
+ * (`parser_init`) and looping (`parser_next`).
+ *
+ * @param opt The The `cli_opt` information that failed parsing
+ * @param specs A NULL-terminated array of `cli_opt_spec`s that can be parsed
+ * @param args The arguments that will be parsed
+ * @param args_len The length of arguments to be parsed
+ * @param flags The `cli_opt_flag_t flags for parsing
+ */
+cli_opt_status_t cli_opt_parse(
+    cli_opt *opt,
+    const cli_opt_spec specs[],
+    char **args,
+    size_t args_len,
+    unsigned int flags);
+
+/**
+ * Initializes a parser that parses the given arguments according to the
+ * given specifications.
+ *
+ * @param parser The `cli_opt_parser` that will be initialized
+ * @param specs A NULL-terminated array of `cli_opt_spec`s that can be parsed
+ * @param args The arguments that will be parsed
+ * @param args_len The length of arguments to be parsed
+ * @param flags The `cli_opt_flag_t flags for parsing
+ */
+void cli_opt_parser_init(
+	cli_opt_parser *parser,
+	const cli_opt_spec specs[],
+	char **args,
+	size_t args_len,
+	unsigned int flags);
+
+/**
+ * Parses the next command-line argument and places the information about
+ * the argument into the given `opt` data.
+ *
+ * @param opt The `cli_opt` information parsed from the argument
+ * @param parser An `cli_opt_parser` that has been initialized with
+ *        `cli_opt_parser_init`
+ * @return true if the caller should continue iterating, or 0 if there are
+ *         no arguments left to process.
+ */
+cli_opt_status_t cli_opt_parser_next(
+	cli_opt *opt,
+	cli_opt_parser *parser);
+
+/**
+ * Prints the status after parsing the most recent argument.  This is
+ * useful for printing an error message when an unknown argument was
+ * specified, or when an argument was specified without a value.
+ *
+ * @param file The file to print information to
+ * @param command The name of the command to use when printing (optional)
+ * @param opt The option that failed to parse
+ * @return 0 on success, -1 on failure
+ */
+int cli_opt_status_fprint(
+	FILE *file,
+	const char *command,
+	const cli_opt *opt);
+
+#endif /* CLI_opt_h__ */
diff --git a/src/cli/opt_usage.c b/src/cli/opt_usage.c
new file mode 100644
index 0000000..478b416
--- /dev/null
+++ b/src/cli/opt_usage.c
@@ -0,0 +1,194 @@
+/*
+ * Copyright (C) the libgit2 contributors. All rights reserved.
+ *
+ * This file is part of libgit2, distributed under the GNU GPL v2 with
+ * a Linking Exception. For full terms see the included COPYING file.
+ */
+
+#include "cli.h"
+#include "str.h"
+
+static int print_spec_name(git_str *out, const cli_opt_spec *spec)
+{
+	if (spec->type == CLI_OPT_TYPE_VALUE && spec->alias &&
+	    !(spec->usage & CLI_OPT_USAGE_VALUE_OPTIONAL) &&
+	    !(spec->usage & CLI_OPT_USAGE_SHOW_LONG))
+		return git_str_printf(out, "-%c <%s>", spec->alias, spec->value_name);
+	if (spec->type == CLI_OPT_TYPE_VALUE && spec->alias &&
+	    !(spec->usage & CLI_OPT_USAGE_SHOW_LONG))
+		return git_str_printf(out, "-%c [<%s>]", spec->alias, spec->value_name);
+	if (spec->type == CLI_OPT_TYPE_VALUE &&
+	    !(spec->usage & CLI_OPT_USAGE_VALUE_OPTIONAL))
+		return git_str_printf(out, "--%s[=<%s>]", spec->name, spec->value_name);
+	if (spec->type == CLI_OPT_TYPE_VALUE)
+		return git_str_printf(out, "--%s=<%s>", spec->name, spec->value_name);
+	if (spec->type == CLI_OPT_TYPE_ARG)
+		return git_str_printf(out, "<%s>", spec->value_name);
+	if (spec->type == CLI_OPT_TYPE_ARGS)
+		return git_str_printf(out, "<%s>...", spec->value_name);
+	if (spec->type == CLI_OPT_TYPE_LITERAL)
+		return git_str_printf(out, "--");
+	if (spec->alias && !(spec->usage & CLI_OPT_USAGE_SHOW_LONG))
+		return git_str_printf(out, "-%c", spec->alias);
+	if (spec->name)
+		return git_str_printf(out, "--%s", spec->name);
+
+	GIT_ASSERT(0);
+}
+
+/*
+ * This is similar to adopt's function, but modified to understand
+ * that we have a command ("git") and a "subcommand" ("checkout").
+ * It also understands a terminal's line length and wrap appropriately,
+ * using a `git_str` for storage.
+ */
+int cli_opt_usage_fprint(
+	FILE *file,
+	const char *command,
+	const char *subcommand,
+	const cli_opt_spec specs[])
+{
+	git_str usage = GIT_BUF_INIT, opt = GIT_BUF_INIT;
+	const cli_opt_spec *spec;
+	size_t i, prefixlen, linelen;
+	bool choice = false, next_choice = false, optional = false;
+	int error;
+
+	/* TODO: query actual console width. */
+	int console_width = 80;
+
+	if ((error = git_str_printf(&usage, "usage: %s", command)) < 0)
+		goto done;
+
+	if (subcommand &&
+	    (error = git_str_printf(&usage, " %s", subcommand)) < 0)
+		goto done;
+
+	linelen = git_str_len(&usage);
+	prefixlen = linelen + 1;
+
+	for (spec = specs; spec->type; ++spec) {
+		if (!choice)
+			optional = !(spec->usage & CLI_OPT_USAGE_REQUIRED);
+
+		next_choice = !!((spec + 1)->usage & CLI_OPT_USAGE_CHOICE);
+
+		if (spec->usage & CLI_OPT_USAGE_HIDDEN)
+			continue;
+
+		if (choice)
+			git_str_putc(&opt, '|');
+		else
+			git_str_clear(&opt);
+
+		if (optional && !choice)
+			git_str_putc(&opt, '[');
+		if (!optional && !choice && next_choice)
+			git_str_putc(&opt, '(');
+
+		if ((error = print_spec_name(&opt, spec)) < 0)
+			goto done;
+
+		if (!optional && choice && !next_choice)
+			git_str_putc(&opt, ')');
+		else if (optional && !next_choice)
+			git_str_putc(&opt, ']');
+
+		if ((choice = next_choice))
+			continue;
+
+		if (git_str_oom(&opt)) {
+			error = -1;
+			goto done;
+		}
+
+		if (linelen > prefixlen &&
+		    console_width > 0 &&
+		    linelen + git_str_len(&opt) + 1 > (size_t)console_width) {
+			git_str_putc(&usage, '\n');
+
+			for (i = 0; i < prefixlen; i++)
+				git_str_putc(&usage, ' ');
+
+			linelen = prefixlen;
+		} else {
+			git_str_putc(&usage, ' ');
+			linelen += git_str_len(&opt) + 1;
+		}
+
+		git_str_puts(&usage, git_str_cstr(&opt));
+
+		if (git_str_oom(&usage)) {
+			error = -1;
+			goto done;
+		}
+	}
+
+	error = fprintf(file, "%s\n", git_str_cstr(&usage));
+
+done:
+	error = (error < 0) ? -1 : 0;
+
+	git_str_dispose(&usage);
+	git_str_dispose(&opt);
+	return error;
+}
+
+int cli_opt_usage_error(
+	const char *subcommand,
+	const cli_opt_spec specs[],
+	const cli_opt *invalid_opt)
+{
+	cli_opt_status_fprint(stderr, PROGRAM_NAME, invalid_opt);
+	cli_opt_usage_fprint(stderr, PROGRAM_NAME, subcommand, specs);
+	return CLI_EXIT_USAGE;
+}
+
+int cli_opt_help_fprint(
+	FILE *file,
+	const cli_opt_spec specs[])
+{
+	git_str help = GIT_BUF_INIT;
+	const cli_opt_spec *spec;
+	int error = 0;
+
+	/* Display required arguments first */
+	for (spec = specs; spec->type; ++spec) {
+		if (! (spec->usage & CLI_OPT_USAGE_REQUIRED) ||
+		    (spec->usage & CLI_OPT_USAGE_HIDDEN))
+			continue;
+
+		git_str_printf(&help, "    ");
+
+		if ((error = print_spec_name(&help, spec)) < 0)
+			goto done;
+
+		git_str_printf(&help, ": %s\n", spec->help);
+	}
+
+	/* Display the remaining arguments */
+	for (spec = specs; spec->type; ++spec) {
+		if ((spec->usage & CLI_OPT_USAGE_REQUIRED) ||
+		    (spec->usage & CLI_OPT_USAGE_HIDDEN))
+			continue;
+
+		git_str_printf(&help, "    ");
+
+		if ((error = print_spec_name(&help, spec)) < 0)
+			goto done;
+
+		git_str_printf(&help, ": %s\n", spec->help);
+
+	}
+
+	if (git_str_oom(&help) ||
+	    p_write(fileno(file), help.ptr, help.size) < 0)
+		error = -1;
+
+done:
+	error = (error < 0) ? -1 : 0;
+
+	git_str_dispose(&help);
+	return error;
+}
+
diff --git a/src/cli/opt_usage.h b/src/cli/opt_usage.h
new file mode 100644
index 0000000..c752494
--- /dev/null
+++ b/src/cli/opt_usage.h
@@ -0,0 +1,35 @@
+/*
+ * Copyright (C) the libgit2 contributors. All rights reserved.
+ *
+ * This file is part of libgit2, distributed under the GNU GPL v2 with
+ * a Linking Exception. For full terms see the included COPYING file.
+ */
+
+#ifndef CLI_opt_usage_h__
+#define CLI_opt_usage_h__
+
+/**
+ * Prints usage information to the given file handle.
+ *
+ * @param file The file to print information to
+ * @param command The name of the command to use when printing
+ * @param subcommand The name of the subcommand (eg "checkout") to use when printing, or NULL to skip
+ * @param specs The specifications allowed by the command
+ * @return 0 on success, -1 on failure
+ */
+int cli_opt_usage_fprint(
+	FILE *file,
+	const char *command,
+	const char *subcommand,
+	const cli_opt_spec specs[]);
+
+int cli_opt_usage_error(
+	const char *subcommand,
+	const cli_opt_spec specs[],
+	const cli_opt *invalid_opt);
+
+int cli_opt_help_fprint(
+	FILE *file,
+	const cli_opt_spec specs[]);
+
+#endif /* CLI_opt_usage_h__ */
diff --git a/src/cli/progress.c b/src/cli/progress.c
new file mode 100644
index 0000000..ddfbafb
--- /dev/null
+++ b/src/cli/progress.c
@@ -0,0 +1,346 @@
+/*
+ * Copyright (C) the libgit2 contributors. All rights reserved.
+ *
+ * This file is part of libgit2, distributed under the GNU GPL v2 with
+ * a Linking Exception. For full terms see the included COPYING file.
+ */
+
+#include <stdio.h>
+#include <stdarg.h>
+#include <stdint.h>
+
+#include "progress.h"
+#include "error.h"
+
+/*
+ * Show updates to the percentage and number of objects received
+ * separately from the throughput to give an accurate progress while
+ * avoiding too much noise on the screen. (In milliseconds.)
+ */
+#define PROGRESS_UPDATE_TIME    60
+#define THROUGHPUT_UPDATE_TIME 500
+
+#define is_nl(c) ((c) == '\r' || (c) == '\n')
+
+#define return_os_error(msg) do { \
+	git_error_set(GIT_ERROR_OS, "%s", msg); return -1; } while(0)
+
+GIT_INLINE(size_t) no_nl_len(const char *str, size_t len)
+{
+	size_t i = 0;
+
+	while (i < len && !is_nl(str[i]))
+		i++;
+
+	return i;
+}
+
+GIT_INLINE(size_t) nl_len(bool *has_nl, const char *str, size_t len)
+{
+	size_t i = no_nl_len(str, len);
+
+	*has_nl = false;
+
+	while (i < len && is_nl(str[i])) {
+		*has_nl = true;
+		i++;
+	}
+
+	return i;
+}
+
+static int progress_write(cli_progress *progress, bool force, git_str *line)
+{
+	bool has_nl;
+	size_t no_nl = no_nl_len(line->ptr, line->size);
+	size_t nl = nl_len(&has_nl, line->ptr + no_nl, line->size - no_nl);
+	uint64_t now = git_time_monotonic();
+	size_t i;
+
+	/* Avoid spamming the console with progress updates */
+	if (!force && line->ptr[line->size - 1] != '\n' && progress->last_update) {
+		if (now - progress->last_update < PROGRESS_UPDATE_TIME) {
+			git_str_clear(&progress->deferred);
+			git_str_put(&progress->deferred, line->ptr, line->size);
+			return git_str_oom(&progress->deferred) ? -1 : 0;
+		}
+	}
+
+	/*
+	 * If there's something on this line already (eg, a progress line
+	 * with only a trailing `\r` that we'll print over) then we need
+	 * to really print over it in case we're writing a shorter line.
+	 */
+	if (printf("%.*s", (int)no_nl, line->ptr) < 0)
+		return_os_error("could not print status");
+
+	if (progress->onscreen.size) {
+		for (i = no_nl; i < progress->onscreen.size; i++) {
+			if (printf(" ") < 0)
+				return_os_error("could not print status");
+		}
+	}
+
+	if (printf("%.*s", (int)nl, line->ptr + no_nl) < 0 ||
+	    fflush(stdout) != 0)
+		return_os_error("could not print status");
+
+	git_str_clear(&progress->onscreen);
+
+	if (line->ptr[line->size - 1] == '\n') {
+		progress->last_update = 0;
+	} else {
+		git_str_put(&progress->onscreen, line->ptr, line->size);
+		progress->last_update = now;
+	}
+
+	git_str_clear(&progress->deferred);
+	return git_str_oom(&progress->onscreen) ? -1 : 0;
+}
+
+static int progress_printf(cli_progress *progress, bool force, const char *fmt, ...)
+	GIT_FORMAT_PRINTF(3, 4);
+
+int progress_printf(cli_progress *progress, bool force, const char *fmt, ...)
+{
+	git_str buf = GIT_BUF_INIT;
+	va_list ap;
+	int error;
+
+	va_start(ap, fmt);
+	error = git_str_vprintf(&buf, fmt, ap);
+	va_end(ap);
+
+	if (error < 0)
+		return error;
+
+	error = progress_write(progress, force, &buf);
+
+	git_str_dispose(&buf);
+	return error;
+}
+
+static int progress_complete(cli_progress *progress)
+{
+	if (progress->deferred.size)
+		progress_write(progress, true, &progress->deferred);
+
+	if (progress->onscreen.size)
+		if (printf("\n") < 0)
+			return_os_error("could not print status");
+
+	git_str_clear(&progress->deferred);
+	git_str_clear(&progress->onscreen);
+	progress->last_update = 0;
+	progress->action_start = 0;
+	progress->action_finish = 0;
+
+	return 0;
+}
+
+GIT_INLINE(int) percent(size_t completed, size_t total)
+{
+	if (total == 0)
+		return (completed == 0) ? 100 : 0;
+
+	return (int)(((double)completed / (double)total) * 100);
+}
+
+int cli_progress_fetch_sideband(const char *str, int len, void *payload)
+{
+	cli_progress *progress = (cli_progress *)payload;
+	size_t remain;
+
+	if (len <= 0)
+		return 0;
+
+	/* Accumulate the sideband data, then print it line-at-a-time. */
+	if (git_str_put(&progress->sideband, str, len) < 0)
+		return -1;
+
+	str = progress->sideband.ptr;
+	remain = progress->sideband.size;
+
+	while (remain) {
+		bool has_nl;
+		size_t line_len = nl_len(&has_nl, str, remain);
+
+		if (!has_nl)
+			break;
+
+		if (line_len < INT_MAX) {
+			int error = progress_printf(progress, true,
+				"remote: %.*s", (int)line_len, str);
+
+			if (error < 0)
+				return error;
+		}
+
+		str += line_len;
+		remain -= line_len;
+	}
+
+	git_str_consume_bytes(&progress->sideband, (progress->sideband.size - remain));
+
+	return 0;
+}
+
+static int fetch_receiving(
+	cli_progress *progress,
+	const git_indexer_progress *stats)
+{
+	char *recv_units[] = { "B", "KiB", "MiB", "GiB", "TiB", NULL };
+	char *rate_units[] = { "B/s", "KiB/s", "MiB/s", "GiB/s", "TiB/s", NULL };
+	uint64_t now, elapsed;
+
+	double recv_len, rate;
+	size_t recv_unit_idx = 0, rate_unit_idx = 0;
+	bool done = (stats->received_objects == stats->total_objects);
+
+	if (!progress->action_start)
+		progress->action_start = git_time_monotonic();
+
+	if (done && progress->action_finish)
+		now = progress->action_finish;
+	else if (done)
+		progress->action_finish = now = git_time_monotonic();
+	else
+		now = git_time_monotonic();
+
+	if (progress->throughput_update &&
+	    now - progress->throughput_update < THROUGHPUT_UPDATE_TIME) {
+		elapsed = progress->throughput_update -
+		          progress->action_start;
+		recv_len = progress->throughput_bytes;
+	} else {
+		elapsed = now - progress->action_start;
+		recv_len = (double)stats->received_bytes;
+
+		progress->throughput_update = now;
+		progress->throughput_bytes = recv_len;
+	}
+
+	rate = elapsed ? recv_len / elapsed : 0;
+
+	while (recv_len > 1024 && recv_units[recv_unit_idx+1]) {
+		recv_len /= 1024;
+		recv_unit_idx++;
+	}
+
+	while (rate > 1024 && rate_units[rate_unit_idx+1]) {
+		rate /= 1024;
+		rate_unit_idx++;
+	}
+
+	return progress_printf(progress, false,
+		"Receiving objects: %3d%% (%d/%d), %.2f %s | %.2f %s%s\r",
+		percent(stats->received_objects, stats->total_objects),
+		stats->received_objects,
+		stats->total_objects,
+		recv_len, recv_units[recv_unit_idx],
+		rate, rate_units[rate_unit_idx],
+		done ? ", done." : "");
+}
+
+static int fetch_resolving(
+	cli_progress *progress,
+	const git_indexer_progress *stats)
+{
+	bool done = (stats->indexed_deltas == stats->total_deltas);
+
+	return progress_printf(progress, false,
+		"Resolving deltas: %3d%% (%d/%d)%s\r",
+		percent(stats->indexed_deltas, stats->total_deltas),
+		stats->indexed_deltas, stats->total_deltas,
+		done ? ", done." : "");
+}
+
+int cli_progress_fetch_transfer(const git_indexer_progress *stats, void *payload)
+{
+	cli_progress *progress = (cli_progress *)payload;
+	int error = 0;
+
+	switch (progress->action) {
+	case CLI_PROGRESS_NONE:
+		progress->action = CLI_PROGRESS_RECEIVING;
+		/* fall through */
+
+	case CLI_PROGRESS_RECEIVING:
+		if ((error = fetch_receiving(progress, stats)) < 0)
+			break;
+
+		/*
+		 * Upgrade from receiving to resolving; do this after the
+		 * final call to cli_progress_fetch_receiving (above) to
+		 * ensure that we've printed a final "done" string after
+		 * any sideband data.
+		 */
+		if (!stats->indexed_deltas)
+			break;
+
+		progress_complete(progress);
+		progress->action = CLI_PROGRESS_RESOLVING;
+		/* fall through */
+
+	case CLI_PROGRESS_RESOLVING:
+		error = fetch_resolving(progress, stats);
+		break;
+
+	default:
+		/* should not be reached */
+		GIT_ASSERT(!"unexpected progress state");
+	}
+
+	return error;
+}
+
+void cli_progress_checkout(
+	const char *path,
+	size_t completed_steps,
+	size_t total_steps,
+	void *payload)
+{
+	cli_progress *progress = (cli_progress *)payload;
+	bool done = (completed_steps == total_steps);
+
+	GIT_UNUSED(path);
+
+	if (progress->action != CLI_PROGRESS_CHECKING_OUT) {
+		progress_complete(progress);
+		progress->action = CLI_PROGRESS_CHECKING_OUT;
+	}
+
+	progress_printf(progress, false,
+		"Checking out files: %3d%% (%" PRIuZ "/%" PRIuZ ")%s\r",
+		percent(completed_steps, total_steps),
+		completed_steps, total_steps,
+		done ? ", done." : "");
+}
+
+int cli_progress_abort(cli_progress *progress)
+{
+	if (progress->onscreen.size > 0 && printf("\n") < 0)
+	    return_os_error("could not print status");
+
+	return 0;
+}
+
+int cli_progress_finish(cli_progress *progress)
+{
+	int error = progress->action ? progress_complete(progress) : 0;
+
+	progress->action = 0;
+	return error;
+}
+
+void cli_progress_dispose(cli_progress *progress)
+{
+	if (progress == NULL)
+		return;
+
+	git_str_dispose(&progress->sideband);
+	git_str_dispose(&progress->onscreen);
+	git_str_dispose(&progress->deferred);
+
+	memset(progress, 0, sizeof(cli_progress));
+}
diff --git a/src/cli/progress.h b/src/cli/progress.h
new file mode 100644
index 0000000..886fef8
--- /dev/null
+++ b/src/cli/progress.h
@@ -0,0 +1,117 @@
+/*
+ * Copyright (C) the libgit2 contributors. All rights reserved.
+ *
+ * This file is part of libgit2, distributed under the GNU GPL v2 with
+ * a Linking Exception. For full terms see the included COPYING file.
+ */
+
+#ifndef CLI_progress_h__
+#define CLI_progress_h__
+
+#include <git2.h>
+#include "str.h"
+
+/*
+ * A general purpose set of progress printing functions.  An individual
+ * `cli_progress` object is capable of displaying progress for a single
+ * function, even if that function displays multiple pieces of progress
+ * (like `git_clone`).  `cli_progress_finish` should be called after
+ * any function invocation to re-set state.
+ */
+
+typedef enum {
+	CLI_PROGRESS_NONE,
+	CLI_PROGRESS_RECEIVING,
+	CLI_PROGRESS_RESOLVING,
+	CLI_PROGRESS_CHECKING_OUT
+} cli_progress_t;
+
+typedef struct {
+	cli_progress_t action;
+
+	/* Actions may time themselves (eg fetch) but are not required to */
+	uint64_t action_start;
+	uint64_t action_finish;
+
+	/* Last console update, avoid too frequent updates. */
+	uint64_t last_update;
+
+	/* Accumulators for partial output and deferred updates. */
+	git_str sideband;
+	git_str onscreen;
+	git_str deferred;
+
+	/* Last update about throughput */
+	uint64_t throughput_update;
+	double throughput_bytes;
+} cli_progress;
+
+#define CLI_PROGRESS_INIT { 0 }
+
+/**
+ * Prints sideband data from fetch to the console.  Suitable for a
+ * `sideband_progress` callback for `git_fetch_options`.
+ *
+ * @param str The sideband string
+ * @param len The length of the sideband string
+ * @param payload A pointer to the cli_progress
+ * @return 0 on success, -1 on failure
+ */
+extern int cli_progress_fetch_sideband(
+	const char *str,
+	int len,
+	void *payload);
+
+/**
+ * Prints fetch transfer statistics to the console.  Suitable for a
+ * `transfer_progress` callback for `git_fetch_options`.
+ *
+ * @param stats The indexer stats
+ * @param payload A pointer to the cli_progress
+ * @return 0 on success, -1 on failure
+ */
+extern int cli_progress_fetch_transfer(
+	const git_indexer_progress *stats,
+	void *payload);
+
+/**
+ * Prints checkout progress to the console.  Suitable for a
+ * `progress_cb` callback for `git_checkout_options`.
+ *
+ * @param path The path being written
+ * @param completed_steps The completed checkout steps
+ * @param total_steps The total number of checkout steps
+ * @param payload A pointer to the cli_progress
+ */
+extern void cli_progress_checkout(
+	const char *path,
+	size_t completed_steps,
+	size_t total_steps,
+	void *payload);
+
+/**
+ * Stop displaying progress quickly; suitable for stopping an application
+ * quickly.  Does not display any lines that were buffered, just gets the
+ * console back to a sensible place.
+ *
+ * @param progress The progress information
+ * @return 0 on success, -1 on failure
+ */
+extern int cli_progress_abort(cli_progress *progress);
+
+/**
+ * Finishes displaying progress; flushes any buffered output.
+ *
+ * @param progress The progress information
+ * @return 0 on success, -1 on failure
+ */
+extern int cli_progress_finish(cli_progress *progress);
+
+/**
+ * Disposes the progress information.
+ *
+ * @param progress The progress information
+ */
+extern void cli_progress_dispose(cli_progress *progress);
+
+#endif /* CLI_progress_h__ */
diff --git a/src/cli/sighandler.h b/src/cli/sighandler.h
new file mode 100644
index 0000000..877223e
--- /dev/null
+++ b/src/cli/sighandler.h
@@ -0,0 +1,20 @@
+/*
+ * Copyright (C) the libgit2 contributors. All rights reserved.
+ *
+ * This file is part of libgit2, distributed under the GNU GPL v2 with
+ * a Linking Exception. For full terms see the included COPYING file.
+ */
+
+#ifndef CLI_sighandler_h__
+#define CLI_sighandler_h__
+
+/**
+ * Sets up a signal handler that will run when the process is interrupted
+ * (via SIGINT on POSIX or Control-C or Control-Break on Windows).
+ *
+ * @param handler The function to run on interrupt
+ * @return 0 on success, -1 on failure
+ */
+int cli_sighandler_set_interrupt(void (*handler)(void));
+
+#endif /* CLI_sighandler_h__ */
diff --git a/src/cli/unix/sighandler.c b/src/cli/unix/sighandler.c
new file mode 100644
index 0000000..6b4982d
--- /dev/null
+++ b/src/cli/unix/sighandler.c
@@ -0,0 +1,36 @@
+/*
+ * Copyright (C) the libgit2 contributors. All rights reserved.
+ *
+ * This file is part of libgit2, distributed under the GNU GPL v2 with
+ * a Linking Exception. For full terms see the included COPYING file.
+ */
+
+#include <stdint.h>
+#include <signal.h>
+#include "git2_util.h"
+#include "cli.h"
+
+static void (*interrupt_handler)(void) = NULL;
+
+static void interrupt_proxy(int signal)
+{
+	GIT_UNUSED(signal);
+	interrupt_handler();
+}
+
+int cli_sighandler_set_interrupt(void (*handler)(void))
+{
+	void (*result)(int);
+
+	if ((interrupt_handler = handler) != NULL)
+		result = signal(SIGINT, interrupt_proxy);
+	else
+		result = signal(SIGINT, SIG_DFL);
+
+	if (result == SIG_ERR) {
+		git_error_set(GIT_ERROR_OS, "could not set signal handler");
+		return -1;
+	}
+
+	return 0;
+}
diff --git a/src/cli/win32/precompiled.c b/src/cli/win32/precompiled.c
new file mode 100644
index 0000000..5f656a4
--- /dev/null
+++ b/src/cli/win32/precompiled.c
@@ -0,0 +1 @@
+#include "precompiled.h"
diff --git a/src/cli/win32/precompiled.h b/src/cli/win32/precompiled.h
new file mode 100644
index 0000000..b0309b8
--- /dev/null
+++ b/src/cli/win32/precompiled.h
@@ -0,0 +1,3 @@
+#include <git2.h>
+
+#include "cli.h"
diff --git a/src/cli/win32/sighandler.c b/src/cli/win32/sighandler.c
new file mode 100644
index 0000000..cc0b646
--- /dev/null
+++ b/src/cli/win32/sighandler.c
@@ -0,0 +1,37 @@
+/*
+ * Copyright (C) the libgit2 contributors. All rights reserved.
+ *
+ * This file is part of libgit2, distributed under the GNU GPL v2 with
+ * a Linking Exception. For full terms see the included COPYING file.
+ */
+
+#include "git2_util.h"
+#include <windows.h>
+
+#include "cli.h"
+
+static void (*interrupt_handler)(void) = NULL;
+
+static BOOL WINAPI interrupt_proxy(DWORD signal)
+{
+	GIT_UNUSED(signal);
+	interrupt_handler();
+	return TRUE;
+}
+
+int cli_sighandler_set_interrupt(void (*handler)(void))
+{
+	BOOL result;
+
+	if ((interrupt_handler = handler) != NULL)
+		result = SetConsoleCtrlHandler(interrupt_proxy, FALSE);
+	else
+		result = SetConsoleCtrlHandler(NULL, FALSE);
+
+	if (!result) {
+		git_error_set(GIT_ERROR_OS, "could not set control control handler");
+		return -1;
+	}
+
+	return 0;
+}