Bug was this sequence:
1. old sdkconfig file has some settings (maybe target=esp32s2beta)
2. idf.py builds a new sdkconfig.defaults file with full new settings
3. new settings includes something that conflicts with the old settings (for example,
CONFIG_IDF_TARGET=esp32 and BT_ENABLE=y)
4. confgen tries to apply the new "defaults" to the existing sdkconfig, settings end up a mix of both due to the conflicts
Fix is to generate the sdkconfig file directly.
Changes argument parsing mechanism from argparse to a new one, that provides better support for extensions and options that are only applicable to specific subcommands,
Breaking changes:
1. All global options should go before subcommands, i.e. `idf.py build -C ~/some/project` will not work anymore, only `idf.py -C ~/some/project build` is acceptable
2. To provide multiple values to an option like `--define-cache-entry` it's necessary to repeat option many times, i.e. `idf.py -D entry1 entry2 entry3` will not work, right way is: `idf.py -D entry1 -D entry2 -D entry3`
At the moment there are 3 options like this: `--define-cache-entry` in base list and `--test-components` and `--test-exclude-components` in the unit test extensions
3. Drops `defconfig` and `bootloader-clean` subcommands
Closes https://github.com/espressif/esp-idf/issues/3570
Closes https://github.com/espressif/esp-idf/issues/3571
