cargo semver does not pass extra options to cargo

[whentze]

The usage message for cargo semver states:

usage: cargo semver [options] [-- cargo options]

However, additional options after -- are not passed on to cargo.
We should either make that work again or fix the usage message.

[ibabushkin]

Alright, so juding by the state of things in cargo, we cannot pass the free strings left over from command line parsing to cargo since we are not shelling out. So for now I'll just add a disclaimer that this feature does not work and see if we can get it in a different way.

[ibabushkin]

To unroll this further: What kind of flags do we actually need to support currently?

• feature flags (Feature flag support #91)
• offline mode (Offline mode #26)
• workspace-related configuration (Semver doesn't seem to handle multiple-workspace projects well #67)
  • package selectors
• target selection
• unstable flags

Most of these already have an issue and have clear-cut, relatively stable requirements. I currently cannot think of other flags we might want to support, but so far, I'd be in favor of implementing these features locally (including command line parsing) and then to reevaluate whether we want to refactor those bits to push that into cargo.