use arg bin "Name" for install from git

[dpurfield]

This is to address fixes #4830.

I left existing functionality which uses crate arg when present. But when crate is not present and bin name is specified it will now use the provided bin name.

I was going to fix the bins arg which is also not working but that proved to be significantly harder, and this is my first contribution.

[rust-highfive]

Thanks for the pull request, and welcome! The Rust team is excited to review your changes, and you should hear from @Eh2406 (or someone else) soon.

If any changes to this PR are deemed necessary, please add them as extra commits. This ensures that the reviewer can see what has changed since they last reviewed the code. Due to the way GitHub handles out-of-date commits, this should also make it reasonably obvious what issues have or haven't been addressed. Large or tricky changes may require several passes of review and changes.

Please see the contribution instructions for more information.

[alexcrichton]

Thanks for the PR! I don't think this is what the --bin flag is intended for, though. The --bin flag is intended to select binary targets within a package, whereas the "crate" arguments are used to select packages.

[dpurfield]

Ok, I don't think i fully understood the difference between a package and bin. So in the git repo https://github.com/RazrFalcon/svgcleaner, I was treating each package/toml in the repo as a binary. Now i think your saying they are separate packages, because they have there own toml file? If this is true then, then the correct fix is to just state when a repo with multiple packages is referenced, that the package needs to be specified? Or should it just default to the root package?

[dpurfield]

I'm going to close/cancel this PR and discuss some suggestions in the issue 4830 page.