Add --dry-run option to maturin-publish command

[MarTango]

Similar to poetry's publish command, I think it would be cool if a --dry-run option was added which performed all steps except actually uploading build artifacts.

[ChillFish8]

Correct me if im wrong but isnt that the whole purpose of maturing develop [options]

[MarTango]

I'd say that the closest command to this would be maturin build. publish takes the wheels and uploads to a python package repository. I created this issue because I was trying to figure out how to publish to a private package repository and didn't want to actually push anything.

In the end the issue I was coming across was due to the server not supporting the format that maturin publishes in, so a --dry-run option wouldn't have actually been helpful.

I'll leave this issue and a developer who's worked on the publish command can determine whether this would be a useful feature or not.

[konstin]

I fear there isn't much maturin can do here. publish essentially calls build, gets the credentials and then makes one http request per file to upload. The upload api doesn't have a feature to tell the server to validate the upload without actually publishing it.

[programmerjake]

Somewhat related: pypi/warehouse#726