Make CLI more extensible
I'd like to integrate alembic into a larger CMS-like system. For this, the fact that config.main requires either that the user specify a ini file, or that such a file exist in the current directory, is not very helpful. I need to duplicate the entirety of config.main to get rid of this.
I want to propose a patch which separates the command line parsing from the actual execution, such that a custom config object can be used.
It would be even better if a config option could be passed to the CLI code, and if so, the -c option is simply removed, but the rest works as-is.