konsti 317d3dd612 Add test and basic implementation for formatter preview mode (#8044) ... **Summary** Prepare for the black preview style becoming the black stable style at the end of the year. This adds a new test file to compare stable and preview on some relevant preview options in black, and makes `format_dev` understand the black preview flag. I've added poetry as a project that uses preview. I've implemented one specific deviation (collapsing of stub implementation in non-stub files) which showed up in poetry for testing. This also improves poetry compatibility from 0.99891 to 0.99919. Fixes #7440 New compatibility stats: | project | similarity index | total files | changed files | |----------------|------------------:|------------------:|------------------:| | cpython | 0.75803 | 1799 | 1647 | | django | 0.99983 | 2772 | 35 | | home-assistant | 0.99953 | 10596 | 189 | | poetry | 0.99919 | 317 | 12 | | transformers | 0.99963 | 2657 | 332 | | twine | 1.00000 | 33 | 0 | | typeshed | 0.99978 | 3669 | 20 | | warehouse | 0.99969 | 654 | 15 | | zulip | 0.99970 | 1459 | 22 |		2023-10-26 15:33:26 +00:00
..
test/fixtures	Add test and basic implementation for formatter preview mode (#8044)	2023-10-26 15:33:26 +00:00