Handling untracked files

[casio]

Using darker on a repo with as of yet untracked files raises eg.:
fatal: path 'new.py' exists on disk, but not in 'HEAD'

Steps to reproduce

$ mkdir /tmp/test
$ cd /tmp/test
$ git init
$ echo "print('legacy!')" > legacy.py
$ git add .
$ git commit -m 'initial commit'

$ echo "print('new stuff!')" > new.py
$ darker .
fatal: path 'new.py' exists on disk, but not in 'HEAD'

I guess this might be known and intended behavior, but it would be super useful if in a legacy codebase we could just use the same formatting/linting command also for new files added.

Are there any plans to support this usecase?

[akaihola]

Hi @casio, thanks for your well-written issue!

The error message fatal: path 'new.py' exists on disk, but not in 'HEAD' comes from Git when Darker runs

git show HEAD:./new.py

If you run darker -vv --diff . you'll see in more detail what happens behind the scenes. Darker will also output a diff of the reformattings instead of modifying the files, so it's easier to see that it actually still works despite the Git error.

It would probably be a good idea for Darker to look at Git output, and detect and suppress this particular message since it is in fact expected. Or what do you think?

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By the way, there's also a somewhat related pull request #55 which fixes Darker when linter output refers to files which don't currently exist on disk.

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As a side note, we have multiple pull requests which could use a review. Since current contributors are really busy, we'd appreciate help reviewing the PRs. Let me know if you're willing to join us!