nix-shell 1.12 (or nix run) can't take drv as argument anymore

[thufschmitt]

nix-shell had the undocumented but nice feature of being able to be called with directly a drv file as argument. The new version of the tool isn't able to do this anymore, which removes some usages and breaks some workflows

[zimbatm]

The main use-case is something like https://github.com/direnv/direnv/wiki/Nix#persistent-shell where the .drv is added as a new GC root. This allows to reload the same nix-shell environment even if the input files have changed side, like the nix-channel being updated.