apply black only on modifed lines.

POC, still a lot of work.

what

darken --since <git commitish>

Will (try to) reformat only modified lines since <commit-ish>

or

darken --range 12-34,64-67 foo.py

Should only reformat line 12-34 and 64-67 of foo.py.

how

Looking at black internal it seem relatively hard to pass a flag tell it to only refactor some nodes. But, black support fmt:on/off comments;

So this :

• insert comments;
• apply black
• remove the comments it added.
• TADA (TM)

Long term API design:

Get - some – integration with git; I'm thinking something along:

$ darken --since <commitish>

It would run git in the BG, figure out which files and which lines have changed and apply to black to relevant lines.

I'm thinking that if the changed lines represent a significant portion of the file we could expand what need to be reformatted. Th metric for this need to be determined. I prefer the $ darken --since to a $ darken <a given commit only> as it will correctly handle many things like merges, multipple-commits branches...etc.

Issues:

This is an issue:

https://github.com/python/black/issues/560