import-flake: detect default branches correctly

[stuebinm]

See #113

Previously, npins import-flake would simply assume that the branch was called master if not given, which is not correct; nix flakes will use the remote's default branch in such cases.

This mimics the behaviour in the flake importer — however, perhaps it might be better to move it into the Pin struct itself, allowing branch pins with no explicit branch name given, which then resolve to the remote's default branch instead?

[KiaraGrouwstra]

thanks! this indeed addresses #113 for me ✌️

[piegamesde]

however, perhaps it might be better to move it into the Pin struct itself, allowing branch pins with no explicit branch name given, which then resolve to the remote's default branch instead?

how would that look like, UI wise? Because currently the default is to use a release, and a branch is only used when one is specified. So unclear how it would fit in

[stuebinm]

I haven't thought about it in detail — perhaps we could have something like npins add git <url> --default-branch.

I'm not overlay attached to the idea and have little opinion on whether we want to have it or not, but I wanted to mention it here since it's a bit of a "low-hanging fruit" to add, should it be something people are interested in having (e.g. one might argue nix flakes do this, so we want this too, etc.)