Callbacks for Revise events (error, success)

[essenciary]

Currently Revise throws an exception when code can not be revised due to a bug in the application. From that point on, the app does not update anymore (it's not re-compiled) until the issue is fixed. However, if the issue is fixed and Revise is successful, Revise does not log the successful post-error revision.

In my case I'm interested in building development tools for Julia - and a common issue is that people miss Revise errors in the logs and don't realise that their code is no longer being recompiled. I can surface a big error when Revise errors out, by pulling it out from the logs. However, I can't hide the error as Revise does not notify when the problem was fixed.

In general, it would be great to be able to register handlers when revision fails or succeeds - together with the extra information, like the names of the revised/broken files.