Semantic error messages

[rarkins]

I'd like for our error handling to be more robust and thinking of ways in which we can control:

• Errors which mean we should abort the whole run (e.g. disk space, authorization)
• Errors which mean we should abort the repo (config error, git changed, etc)
• Errors which mean we should abort the branch (e.g. PR we thought is open is actually closed)

One possibility would be that instead of throwing new Error(X) we could have classes of errors e.g. mapped to the above. Something like this could mean we have less string-checking of error messages in our error handling and instead can know whether to pass it up or log and consume it.

Another thing I need from the app perspective is to know which repo-level errors are "permanent" - e.g. disabled by config, a fork, etc.

[rarkins]

https://github.com/ehmicky/modern-errors