## To do
- [ ] both files must be strictly identical
- [ ] same permissions as the source file
- [ ] same access/modification times as the source file
- [ ] keep symlinks and hardlinks
- [ ] only copy the parts that are different between the source file and the destination file
## Module
### argparse
module help you easy to use arguments
1. show syntax
2. show information of action
3. show argument need
#
- [ ] os.difflib use for check different
- [ ] os.symlink, os.link, os.readlink, os.unlink for symlinks or hardlinks
- [ ] os.utime, os.chmod for permission and modification time
- [ ] os.open, os.read, os.write, os.sendfile, os.lseek for open, read, write file ...
- [ ] os.path for finding subdirectory
- [ ] os.scandir ...
- [ ] os.stat ...
- [ ] hashlib for check sum md5