ENH: incremental changes to modify only code neighboring already changed lines

[mattip]

Idea: allow running black with a -n --dry-run=filename option and store the resulting changeset. Then allow using this in a subsequent run to only update newly found changes.

Rational: In a workflow on an established managed repository, this would allow running black incrementally, reformatting only parts of the code that have been changed, minimizing git churn and blame lines.

[ambv]

This is something we explicitly don't support. Incremental style changes are against PEP 8's philosophy of staying consistent within a file. They also mix formatting changes with semantic changes, making review harder than it needs to be. See #134 for a longer explanation.

Reformat your entire project in one go. Then there is a single commit that is trivial to omit using git hyper-blame or simply by using git blame $BLACK_COMMIT^ -- $FILE. It's a cleaner approach than trying to smear adoption over time.

See also: #320

[wbolster]

fyi, i wrote https://github.com/wbolster/black-macchiato

[akaihola]

Also FYI, I wrote darker for applying Black formatting only to lines which have changed in the Git working tree since the last commit.