hy-util: support missing outvars in hy_split_nevra and add hy_parse_module_spec

[jlebon]

commit f814dda7b87201800e0ffa8abd4fdd4c9f021697
Date:   Fri Apr 23 12:08:34 2021 -0400

    hy-util: support missing outvars in hy_split_nevra

    Often, the client-side is only interested in e.g. extracting the package
    name, or the NVR, from a NEVRA. Let's make that easier by not requiring
    them to specify output variables for the components they're not
    interested in.

    = changelog =
    msg: Allow omitting some output variables when calling hy_split_nevra()
    type: enhancement

commit 2dd667f1ba0ffccc3c14f8c7fbe7aee27ad9e1b9
Date:   Fri Apr 23 12:10:24 2021 -0400

    hy-util: add hy_parse_module_spec

    This is a simple wrapper around libdnf::Nsvcap's `parse()` function.
    Support missing output variables, just like `hy_split_nevra`.

    = changelog =
    msg: Add new API hy_parse_module_spec()
    type: enhancement

[jlebon]

Wasn't sure if to add a docstring here. I can do so, but was keying off the other functions in this file not having one.

[Conan-Kudo]

This should be named hy_split_nsvcap with the first parameter being named *nsvcap. That makes it consistent with the other one that does the same thing for packages.

[jlebon]

hy_split_nevra takes a NEVRA and splits it into its components. hy_parse_module_spec takes a module spec and tries it on various forms until it gets a match before splitting into its components. Hence why they're named differently. One could imagine a hy_split_nsvcap which assumes an NSVCAP as its first argument, analogous to hy_split_nevra.

[Conan-Kudo]

But this does effectively assume that you're passing NSVCAP to it, because it does the same splitting.

[jlebon]

No, it would parse e.g. foobar:1.2 just fine. Unspecified components are returned as empty strings. Open to change that to just leave them NULL instead.

[jlebon]

With the final rework in #1207, we no longer need this. The first commit still makes sense I think, but meh... not worth the churn.