dryrun option is a little misleading

[deinspanjer]

I'd expect using dryrun to output a list of all the changes it would make but not make them.
Reviewing the code, it appears that dryrun is effectively a no-op for modifying tables. It doesn't output the differences.

If the code were refactored for this, you could also easily make the app have an interactive mode where it would list the proposed changes and ask the user to confirm before starting. Nice for people who are worried about the behavior.