Allow semver constraints when installing packages

[Michael-F-Bryan]

Motivation

Sometimes, instead of installing a package's exact version, you only care about something "compatible" with that version. It'd be nice if we can run wapm install Michael-F-Bryan/hello-world@^0.2 to get a version of Michael-F-Bryan/hello-world that satisfies the semver constraint, ^0.2.0 (i.e. 0.2.5, but not 0.3.0).

For a more concrete example, on the WAPM backend @ayys and I want to be able to automatically pick up bugfixes to wit-pack as they are released while preventing breaking changes from being installed like you would get from a naive wapm install Michael-F-Bryan/hello-world.

Proposed solution

In theory, this should just be a case of updating AddedPackages::extract_name_and_version() to return a VersionReq here

wapm-cli/src/dataflow/added_packages.rs

Lines 57 to 61 in 6b7d7f1

	fn extract_name_and_version(pair: (&'a str, &'a str)) -> Result<(&'a str, Version), Error> {
	Version::parse(pair.1)
	.map(|version| (pair.0, version))
	.map_err(|e| Error::SemVerError(e.to_string()))
	}

Then, this line would call PackageKey::new_registry_package_range(n, v) instead of PackageKey::new_registry_package(n, v).

wapm-cli/src/dataflow/added_packages.rs

Line 28 in 6b7d7f1

.map(|(n, v)| PackageKey::new_registry_package(n, v))

Alternatives

One alternative would be to allow people to use a VersionReq with wapm search to find the version compatible with a particular requirement, which would then let you run wapm install package@specific_version like normal. I don't think splitting the operation into two steps would help much, though.