Cargo-edit: Switch to Clap

[killercup]

cargo itself recently switched to clap. I know we've had an issue open before about switching away from doctopt and closed it because we wanted to be able to integrate cargo-edit into cargo at some point. Guess we can actually get rid of docopt in good conscience now!

[kbknapp]

I've got this basically implemented, just need to convert the final few tests.

It's essentially a 1:1 port where the only difference is clap enforcing some of the constraints instead of cargo-edit.

The only user facing difference is when using --upgrade=minor it always uses the prefix ^ instead of "". I kind of prefer the explicitness of this, but if you'd prefer to keep "" as the minor prefix it's a simple change.

[killercup]

@kbknapp awesome! I'm fine with having the explicit ^. @bjgill, @ordian, what do you think?

[ordian]

I don't have a strong opinion on that, but would prefer having ^ only if user specifies --upgrade=minor explicitly.

[kbknapp]

Yeah I should have worded that better, but it sounds like you both picked up on my meaning despite my poor choice of words 😜

For others reading this:

Currently in cargo-edit using nothing for the upgrade method (which defaults to minor) uses a blank prefix of "" (empty string) because to cargo it has the same meaning as explicitly using the ^ prefix. Such as 1.2.3 being equivalent to ^1.2.3. However, if the user specified --upgrade=minor on the command line, it used the explicit ^ prefix.

In the port to clap I used the explicit prefix in both cases, when the user uses --upgrade=minor on the command line and when they use nothing and just lets the default case work.

[DCjanus]

Is that ok if I’d like to replace docopt with structopt, rather than clap?

Obviously, structopt has a better API, ~but I'm not sure if this will hinder the plan that being part of cargo in the future.~ structopt::StructOpt can be easily converted to clap::APP.