Report installed package versions

[olexandr-konovalov]

It will be useful if gpm could produce a report about installed package versions. It could report installed version of the package are reported in PackageInfo.g file and some additional information e.g. the source of installation (came with GAP or was upgraded by gpm; from which location; based on which commit if cloned from a repository, etc.).

This will be helpful e.g. when one needs to reproduce some environment for debugging purposes.

[mtorpey]

This seems like a good idea for the reasons you stated. It would require significant work, but would be helpful in maintaining a library of packages. In particular, when we remove a package, we might want to automatically remove dependencies that were not explicitly requested in their own right (as apt does).