Currently the top-level parsing just uses sys.argv then dispatches to subcommands which each have their own parser constructed with argparse. Although argparse has great aspects, I believe it's a bit tough to build a subcommmand-driven parser with it (thus the current construction I guess).

There are some great-seeming, recently-developed tools capable of implementing a complex CLI like smt. One example is cliff, but click seems more well-supported and documented. (See repo example for a subcommand system.)

Moving to one of these would not only support completion, but could aid long term maintenance and extensibility. For example, at the cost of some UI rigidity, it will make the CLI a little more self-documenting (removing the need for maintaining bin/smt by using entry points and providing top-level options for the smt command). Additionally, click in particular is python 2/3 agnostic so could help ease that transition (though of course the CLI is a very small part of this issue).

(Above first raised in #224 migrated to this new issue)