The only commands of the tool are `help`, `version` and `install`.

gpm does version management by delegating part of the work to `go get` (which actually fetches and installs the Go packages and is part of the Go language) and then using the underlying version control system to set each package to the correct repo - go get simply clones packages from git, mercurial and bazaar as an entire repo.

There is no central package management entity we can query, and not even much behaviour outside of using `go get` and `git checkout` - or the bazaar and mercurial equivalents. 

For reference: [this 40 lines of code](https://github.com/pote/gpm/blob/master/bin/gpm#L39-L77) are the entirety of the executable.