Add config file support

[chrisbouchard]

Add support for configuration files in pyupgrade using ConfigArgParse.

By default, we'll look for a tool.pyupgrade section in pyupgrade.toml or pyproject.toml (in that order), and read the configuration from there. Command line arguments will override configuration file settings, which will override command line argument defaults. We also add a --config-file option to override the config file path.

Fixes #511.

Example Output

% pyupgrade -h
usage: pyupgrade [-h] [--config-file CONFIG_FILE] [--exit-zero-even-if-changed] [--keep-percent-format] [--keep-mock] [--keep-runtime-typing] [--py3-plus]
                 [--py36-plus] [--py37-plus] [--py38-plus] [--py39-plus] [--py310-plus] [--py311-plus] [--py312-plus]
                 [filenames ...]

positional arguments:
  filenames

options:
  -h, --help            show this help message and exit
  --config-file CONFIG_FILE
                        config file path
  --exit-zero-even-if-changed
  --keep-percent-format
  --keep-mock
  --keep-runtime-typing
  --py3-plus, --py3-only
  --py36-plus
  --py37-plus
  --py38-plus
  --py39-plus
  --py310-plus
  --py311-plus
  --py312-plus

Args that start with '--' can also be set in a config file (pyupgrade.toml or pyproject.toml or specified via --config-file). Config file syntax is Tom's
Obvious, Minimal Language. See https://github.com/toml-lang/toml/blob/v0.5.0/README.md for details. In general, command-line values override config file
values which override defaults.

TODO

• [x] Add ConfigArgParse dependency
• [x] Switch from argparse to configargparse
• [ ] Add unit tests for config file parsing
• [ ] Add documentation for config file handling

[asottile]

no thanks, this has been rejected before please search next time

[asottile]

oh you did find the duplicate and decided to waste both of our time anyway