Proposal: nix flake update --exclude

[gekoke]

Is your feature request related to a problem? Please describe.
I would find it very useful if there was a way to update all inputs to a flake, excepting some arbitrary subset.

Currently the only way to do that (AFAIK, correct me if I'm wrong?) is list the desired inputs to update explicitly (i.e. in nix flake update input1 input2 or nix flake lock --update-input input1 input2), or run nix flake update and try to discard the appropriate changes to the lockfile.

Describe the solution you'd like
An option in the CLI to run nix flake update foo bar baz --except baz, which would perform set subtraction from the variable argument list, resulting in the inputs foo, bar being updated. nix flake update --except foo would update all unpinned flake inputs except for foo.

Describe alternatives you've considered
None