This tool creates PRs that bump the Cargo version and update the changelog, you merge them if you want a release done. Then during every merge to master it checks if the version has been updated and if so: (1) verifies there is no semver break, (2) publishes to crates.io, (3) creates a tag, (4) creates a github release.

Not sure how interested you would be, but for a lot of rust-lang/ repos we have appreciated being able to do releases without any local git work.