cargo upgrade should have options to include / exclude semver-incompatible versions

[shepmaster]

When updating my dependencies, I tend to run just plain cargo update as I generally only care about updating my lockfile. About the only time I'm interested in changing the manifest file is when I need to make changes for semver reasons. Specifically, I want to know when a new semver-incompatible version of a dependency has been released and I want to

• Support both the old and the new version
• Support only the new version

The fact that cargo upgrade changes semver-compatible versions is mostly annoying to me — I don't want to force my downstream users to be more tightly constrained than they need to be.

I would propose that an option be added to allow only changing versions of those dependencies where the newer version is not semver compatible with the current version.

[vi]

Workaround: Run cargo update, then cargo outdated -d 1, followed by cargo upgrade <manually specified list from cargo oudated>

[DCjanus]

Shoule be closed by #360