Option to calculate closure impact

[timokau]

The PR template recommends

* Determined the impact on package closure size (by running `nix path-info -S` before and after

It would be nice to have nix-review do that automatically. This may require a second rebuild, so maybe it should be disabled by default. Then again in 99% of the cases the second rebuild would be quick. Maybe it would even be possible to time the changed build first and then decide based on that weather or not to determine closure size.

[Mic92]

Seems like a good idea. I would accept an pull request adding option that performs this. Making the selection of attributes where this calculation is performed, would be reasonable.

[davidak]

This would be helpful!

I had created a shell script to calculate the impact. This can be used to copy the logic.

NixOS/nixpkgs#51368

Making the selection of attributes where this calculation is performed, would be reasonable.

an option is good, but i would prefer also a sane default, like getting the name from the commit title

in most cases the former version can be fetched from hydea. maybe we can just get the size without getting the whole binary?

when a binary is not available and the former build took long, the script could ask if it should build a second time and warn that it could take long

[Mic92]

Asking hydra seems like a good option if that was possible. I could imagine to just display that by default after the other packages have been built.