nix run defaults to master for git+https URLs even when this isn't the remote's HEAD

[remexre]

Describe the bug

nix run (and presumably other Flake-involving commands) should default to using the default branch for git+https URLs, rather than hard-coding master.

I would guess this behavior comes from

nix/src/libfetchers/git.cc

Line 289 in 5c99ec3

if (!input.getRef()) input.attrs.insert_or_assign("ref", isLocal ? readHead(actualUrl) : "master");

, but I'm not familiar with the Nix codebase.

Steps To Reproduce

1. Create a repo with a default branch other than master, and no master branch
2. nix run git+https://...
3. See fatal: couldn't find remote ref refs/heads/master

Expected behavior

The default branch of the remote should be used.

nix-env --version output

nix-env (Nix) 2.4pre20210707_02dd6bb

[abathur]

I am not sure if these just use the short form of fetchGit under the hood, but if so this is probably the same underlying issue as #4456

[stale]

I marked this as stale due to inactivity. → More info