You can indeed reference a git repository with a single commit specified, like described in the npm install docs[1].
Not very user friendly, but it works.
That's a bit too idealistic; in practice, any commit MAY have a bug which passed quality control. The problem is that it's all down to people's discipline, it's not an enforced standard.
A package manager where every release has to be reviewed, tested and approved before they become generally available would be a pretty interesting case, I know bigger companies who are reluctant to upgrade because of known bugs in the past would be willing to pay for something like that.
Or you can tie it to Github and then download a release from their CDN.