Betterer in CI: Fail command if diff is found

[koggdal]

Our situation is that we run Betterer in a pre-commit hook, which then commits the changes to the results file. We also run it in CI. However, if someone skips the pre-commit hooks, it will still run fine in CI, but when the change is merged, running Betterer will generate a diff on master.

Could we get a flag to pass to Betterer to skip writing to file, and fail the command if a diff is found?

Thanks! 🙏

[jLouzado]

Maybe a Github Action instead that detects whether there's a new diff on master and makes a commit? The repo is anyway guarded against a regression, this would just be a convenient thing for everyone.

[phenomnomnominal]

I've got an implementation of this coming ASAP 😄

[phenomnomnominal]

Should be covered by #250! WIll close when I release V4.