Can't write reformatted files for revision 'master'

[d-r-jenkins]

So I am testing darker out, and I can get it to print the diffs I want, but it refuses to apply the changes, giving me

$ darker file1.py --revision HEAD..master
argument -r/--revision: Can't write reformatted files for revision 'master'. Either --diff or --check must be used.

The equivalent of this message comes up regardless of what I put in the --revision flag, I have tried every combination ofmaster, HEAD, and specific git hashes.
The git log of the test repo I am in is:

* bfc508f - Mon, 31 Jul 2023 13:52:49 +0200 (4 days ago) (HEAD -> branch_again)
|           branch_again - Me
* 9f5543f - Mon, 31 Jul 2023 13:37:02 +0200 (4 days ago)
|           branch_again commit - Me
* 6a48fad - Mon, 31 Jul 2023 13:36:26 +0200 (4 days ago)
|           branch_again commit - Me
* f6b863f - Mon, 31 Jul 2023 13:23:04 +0200 (4 days ago) (another_branch)
|           Commit to another_branch - Me
* 5d7ddae - Mon, 31 Jul 2023 13:22:34 +0200 (4 days ago)
|           Commit to another_branch - Me
* d6897ea - Mon, 31 Jul 2023 13:20:53 +0200 (4 days ago) (master)
            Initial commit. - Me

Is there something obvious I am missing?

[akaihola]

Hi @Daniel-Jenkins, thanks for the question!

You probably want to use --revision master..HEAD instead. It's actually equivalent to --revision master.. or just --revision master.

If you had also commits on masterafter the branch point of another_branch, you would want --revision master...HEAD or --revision master.... The three dots will cause Git to find the branch point and compare to that.

Could we improve or correct documentation to make the syntax of --revision more clear?

[d-r-jenkins]

Hi!

Thanks for the answer. I think I was just missing some knowledge about how the notation worked.

In terms of docs, I think something about this error may be useful, since I couldn't find anything about it. I am unsure if I will have time till next week to write anything, and even then I can't promise.