diff --git a/.editorconfig b/.editorconfig
new file mode 100644
index 0000000..de2e132
--- /dev/null
+++ b/.editorconfig
@@ -0,0 +1,17 @@
+root = true
+
+[*]
+end_of_line = lf
+insert_final_newline = true
+charset = utf-8
+trim_trailing_whitespace = true
+indent_style = tab
+tab_width = 2
+
+[*.toml]
+indent_style = space
+indent_size = 4
+
+[*.{yml,yaml}]
+indent_style = space
+indent_size = 2
diff --git a/.pre-commit-config.yaml b/.pre-commit-config.yaml
new file mode 100644
index 0000000..7ac2b46
--- /dev/null
+++ b/.pre-commit-config.yaml
@@ -0,0 +1,32 @@
+default_install_hook_types:
+  - pre-commit
+  - commit-msg
+
+repos:
+  - repo: https://github.com/pre-commit/pre-commit-hooks
+    rev: v4.6.0
+    hooks:
+      - id: trailing-whitespace
+      - id: end-of-file-fixer
+      - id: check-added-large-files
+      - id: check-json
+      - id: check-yaml
+      - id: check-toml
+      - id: check-merge-conflict
+
+  - repo: https://github.com/compilerla/conventional-pre-commit
+    rev: v4.0.0
+    hooks:
+      - id: conventional-pre-commit
+        stages: [commit-msg]
+        args: []
+
+  - repo: https://github.com/astral-sh/ruff-pre-commit
+    rev: v0.6.9
+    hooks:
+      - id: ruff-format
+
+  - repo: https://github.com/editorconfig-checker/editorconfig-checker.python
+    rev: 3.0.3
+    hooks:
+      - id: editorconfig-checker
diff --git a/git-third-party b/git-third-party
index 65d53af..4014f49 100755
--- a/git-third-party
+++ b/git-third-party
@@ -1,135 +1,216 @@
 #!/usr/bin/env python3
 
- #
- # This file is part of the git-third-party distribution (https://github.com/kp2pml30/git-third-party).
- # Copyright (c) 2024 Kira Prokopenko kp2pml30@gmail.com
- #
- # This program is free software: you can redistribute it and/or modify
- # it under the terms of the GNU General Public License as published by
- # the Free Software Foundation, version 3.
- #
- # This program is distributed in the hope that it will be useful, but
- # WITHOUT ANY WARRANTY; without even the implied warranty of
- # MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
- # General Public License for more details.
- #
- # You should have received a copy of the GNU General Public License
- # along with this program. If not, see <http://www.gnu.org/licenses/>.
- #
+#
+# This file is part of the git-third-party distribution (https://github.com/kp2pml30/git-third-party).
+# Copyright (c) 2024 Kira Prokopenko kp2pml30@gmail.com
+#
+# This program is free software: you can redistribute it and/or modify
+# it under the terms of the GNU General Public License as published by
+# the Free Software Foundation, version 3.
+#
+# This program is distributed in the hope that it will be useful, but
+# WITHOUT ANY WARRANTY; without even the implied warranty of
+# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
+# General Public License for more details.
+#
+# You should have received a copy of the GNU General Public License
+# along with this program. If not, see <http://www.gnu.org/licenses/>.
+#
 
 EXE_NAME = 'git third-party'
 
 import subprocess
+import os
+import sys
+import abc
+import typing
+from pathlib import Path
+
+GIT = os.getenv('GIT', 'git')
 
 try:
-	top_dir_str = subprocess.check_output(['git', 'rev-parse', '--show-toplevel'], text=True)
+	top_dir_str = subprocess.check_output(
+		['git', 'rev-parse', '--show-toplevel'], text=True
+	)
 except:
 	exit(1)
 
-from pathlib import Path
-import os
 top_dir = Path(top_dir_str.strip())
 cur_dir = Path(os.getcwd())
 
 config_path = top_dir.joinpath('.gitthirdparty')
 if not config_path.exists():
-	config = {
-		"repos": {}
-	}
+	config = {'repos': {}}
 else:
 	import json
+
 	with open(config_path) as f:
 		config = json.load(f)
 
-import sys
+import textwrap
+import io
+
+
+class Command:
+	name: typing.ClassVar[str]
+	help: str
+
+	@abc.abstractmethod
+	def handle(args: list[str]) -> None: ...
+
+	def show_help(self, file: io.StringIO):
+		file.write(f'subcommand `{self.name}`:')
+		file.write(textwrap.indent(textwrap.dedent(self.help), prefix='\t'))
+
 
 def _get_patches_dir(name: str) -> Path:
 	return top_dir.joinpath('.gitthirdparty-patches', *name.split('/'))
 
+
 def _dirty_check(name: str) -> None:
 	target_dir = top_dir.joinpath(*name.split('/'))
 	for opts in ([], ['--cached']):
-		rs = subprocess.run(['git', 'diff', '--exit-code', '--quiet', *opts], check=False, cwd=target_dir)
+		rs = subprocess.run(
+			['git', 'diff', '--exit-code', '--quiet', *opts], check=False, cwd=target_dir
+		)
 		if rs.returncode != 0:
 			raise GitThirdPartyException(f'repo {name} is dirty ( {target_dir} )')
 
+
 def _update_at(name: str) -> None:
 	conf = config['repos'][name]
 	target_dir = top_dir.joinpath(*name.split('/'))
 	if not target_dir.exists():
 		target_dir.mkdir(parents=True, exist_ok=True)
 		subprocess.run(['git', 'init'], check=True, cwd=target_dir)
-		subprocess.run(['git', 'remote', 'add', 'origin', conf['url']], check=True, cwd=target_dir)
+		subprocess.run(
+			['git', 'remote', 'add', 'origin', conf['url']], check=True, cwd=target_dir
+		)
 
 	_dirty_check(name)
 	rs = subprocess.run(['git', 'checkout', conf['commit']], check=False, cwd=target_dir)
 	if rs.returncode != 0:
-		subprocess.run(['git', 'fetch', 'origin', '--depth=1', conf['commit']], check=True, cwd=target_dir)
+		subprocess.run(
+			['git', 'fetch', 'origin', '--depth=1', conf['commit']],
+			check=True,
+			cwd=target_dir,
+		)
 		subprocess.run(['git', 'checkout', conf['commit']], check=True, cwd=target_dir)
-	subprocess.run(['git', 'submodule', 'update', '--init', '--recursive', '--depth', '1'], check=True, cwd=target_dir)
+	subprocess.run(
+		['git', 'submodule', 'update', '--init', '--recursive', '--depth', '1'],
+		check=True,
+		cwd=target_dir,
+	)
 	submodules = conf.get('submodules', None)
 	if submodules is None:
-		subprocess.run(['git', 'submodule', 'update', '--recursive', '--depth', '1'], check=True, cwd=target_dir)
+		subprocess.run(
+			['git', 'submodule', 'update', '--recursive', '--depth', '1'],
+			check=True,
+			cwd=target_dir,
+		)
 	elif len(submodules) != 0:
-		subprocess.run(['git', 'submodule', 'update', '--recursive', '--depth', '1', '--'] + submodules, check=True, cwd=target_dir)
+		subprocess.run(
+			['git', 'submodule', 'update', '--recursive', '--depth', '1', '--'] + submodules,
+			check=True,
+			cwd=target_dir,
+		)
 	# apply patches
 	patches_dir = _get_patches_dir(name)
 	patch_files = [patches_dir.joinpath(str(i)) for i in range(1, conf['patches'] + 1)]
 	if len(patch_files) != 0:
 		subprocess.run(['git', 'am', *patch_files], cwd=target_dir, check=True)
 
+
 class GitThirdPartyException(Exception):
 	pass
 
+
 def _get_path_rel_to_dir(path: str) -> str:
 	target_dir = cur_dir.joinpath(Path(path))
 	if top_dir not in target_dir.parents:
-		raise GitThirdPartyException(f'target directory ({target_dir}) is not in git subtree ({top_dir})')
+		raise GitThirdPartyException(
+			f'target directory ({target_dir}) is not in git subtree ({top_dir})'
+		)
 	return str(target_dir.relative_to(top_dir)).replace(os.sep, '/')
 
-def add(args: list[str]) -> None:
-	if len(args) != 3:
-		print(f'Expected `{EXE_NAME} add <PATH> <REPO URL> <COMMIT>`, got {args}', file=sys.stderr)
-		exit(1)
-	path, repo, commit = args
-	import re
-	if re.search(r'[\\:;]', path):
-		print(f'bad path {path}', file=sys.stderr)
-		exit(1)
-	name = _get_path_rel_to_dir(path)
-	if name in config['repos']:
-		print(f'repo ({name}) is already in config', file=sys.stderr)
-		exit(1)
-	target_dir = top_dir.joinpath(*name.split('/'))
-	res = subprocess.run(['git', 'check-ignore', target_dir], check=False)
-	if res.returncode != 0:
-		raise GitThirdPartyException(f'target directory ({target_dir}) is not ignored by git')
-	config['repos'][name] = {
-		'url': repo,
-		'commit': commit,
-		'patches': 0,
-	}
-	_update_at(name)
+
+class AddCommand(Command):
+	name = 'add'
+	help = f"""\
+		{EXE_NAME} {name} <PATH> <REPO URL> <COMMIT>
+
+	"""
+
+	def handle(self, args: list[str]) -> None:
+		if len(args) != 3:
+			print(f'Unexpected arguments {args}', file=sys.stderr)
+			self.show_help(sys.stderr)
+			exit(1)
+		path, repo, commit = args
+		import re
+
+		if re.search(r'[\\:;]', path):
+			print(f'bad path `{path}`', file=sys.stderr)
+			exit(1)
+		name = _get_path_rel_to_dir(path)
+		if name in config['repos']:
+			print(f'repo ({name}) is already in config', file=sys.stderr)
+			exit(1)
+		target_dir = top_dir.joinpath(*name.split('/'))
+		res = subprocess.run(['git', 'check-ignore', target_dir], check=False)
+		if res.returncode != 0:
+			raise GitThirdPartyException(
+				f'target directory ({target_dir}) is not ignored by git'
+			)
+		config['repos'][name] = {
+			'url': repo,
+			'commit': commit,
+			'patches': 0,
+		}
+		_update_at(name)
+
 
 def _get_all_names() -> list[str]:
 	return list(config['repos'].keys())
 
+
 def _get_names_from_paths(paths: list[str]) -> list[str]:
 	if len(paths) == 0:
-		raise GitThirdPartyException("excepted non-empty list of arguments")
+		raise GitThirdPartyException('excepted non-empty list of arguments')
 	if paths == ['--all']:
 		return _get_all_names()
 	return list(set(map(_get_path_rel_to_dir, paths)))
 
-def update(args: list[str]) -> None:
-	names = _get_names_from_paths(args)
-	for name in names:
-		_update_at(name)
 
-def save(args: list[str]) -> None:
-	names = _get_names_from_paths(args)
-	for name in names:
-		_save_at(name)
+class UpdateCommand(Command):
+	name = 'update'
+	help = f"""\
+		{EXE_NAME} {name} --all
+		{EXE_NAME} {name} relative/path/to/repo/1 relative/path/to/repo/2
+
+		restore state of specified repositories
+	"""
+
+	def handle(args):
+		names = _get_names_from_paths(args)
+		for name in names:
+			_update_at(name)
+
+
+class SaveCommand(Command):
+	name = 'save'
+	help = f"""\
+		{EXE_NAME} {name} --all
+		{EXE_NAME} {name} relative/path/to/repo/1 relative/path/to/repo/2
+
+		record state of specified repositories
+	"""
+
+	def handle(args):
+		names = _get_names_from_paths(args)
+		for name in names:
+			_save_at(name)
+
 
 def _save_at(name: str) -> None:
 	_dirty_check(name)
@@ -139,35 +220,56 @@ def _save_at(name: str) -> None:
 		patches_dir.joinpath(str(i)).unlink()
 	patches_dir.mkdir(parents=True, exist_ok=True)
 	target_dir = top_dir.joinpath(*name.split('/'))
-	subprocess.run(['git', 'format-patch', f'{conf["commit"]}..HEAD', '--no-numbered', '--zero-commit', '--no-signature', '--numbered-files', '-o', patches_dir], check=True, cwd=target_dir)
-	new_patches = subprocess.run(['git', 'rev-list', '--count', f'{conf["commit"]}..HEAD'], check=True, cwd=target_dir, text=True, capture_output=True)
+	subprocess.run(
+		[
+			'git',
+			'format-patch',
+			f'{conf["commit"]}..HEAD',
+			'--no-numbered',
+			'--zero-commit',
+			'--no-signature',
+			'--numbered-files',
+			'-o',
+			patches_dir,
+		],
+		check=True,
+		cwd=target_dir,
+	)
+	new_patches = subprocess.run(
+		['git', 'rev-list', '--count', f'{conf["commit"]}..HEAD'],
+		check=True,
+		cwd=target_dir,
+		text=True,
+		capture_output=True,
+	)
 	conf['patches'] = int(new_patches.stdout.strip())
 
-modes = {
-	"add": add,
-	"update": update,
-	"save": save,
-	"help": lambda x: show_help(*x, file=sys.stdout, exit_code=0)
-}
 
-def show_help(*args, file=sys.stderr, exit_code=1):
-	if len(args) != 0:
-		print(f"help gets no arguments, got {args}", file=file)
-		exit_code = 1
-	print(f"USAGE: {EXE_NAME} {'|'.join(modes.keys())}", file=file)
-	exit(exit_code)
+mode = sys.argv[1] if len(sys.argv) > 1 else 'help'
 
-mode = sys.argv[1] if len(sys.argv) > 1 else '<not provided>'
-mode_handler = modes.get(mode, None)
+handlers: dict[str, Command] = {}
+
+for c in [UpdateCommand, SaveCommand, AddCommand]:
+	handlers[c.name] = c()
+
+mode_handler = handlers.get(mode, None)
 if mode_handler is None:
-	show_help()
+	print(
+		f'{EXE_NAME} expected one of following subcommands: ' + '|'.join(handlers.keys()),
+		file=sys.stderr,
+	)
+	for k in handlers.values():
+		k.show_help(sys.stderr)
+	exit(1)
+
 try:
-	mode_handler(sys.argv[2:])
+	mode_handler.handle(sys.argv[2:])
 except GitThirdPartyException as e:
 	print(*e.args, file=sys.stderr)
 	exit(1)
 
 import json
+
 with open(config_path, 'wt') as f:
 	json.dump(config, f, indent='\t')
 	f.write('\n')
diff --git a/ruff.toml b/ruff.toml
new file mode 100644
index 0000000..18748aa
--- /dev/null
+++ b/ruff.toml
@@ -0,0 +1,9 @@
+indent-width = 2
+
+[format]
+indent-style = "tab"
+quote-style = "single"
+line-ending = "lf"
+
+skip-magic-trailing-comma = false
+docstring-code-format = true