Function branch 

pub fn branch(primary: &Path, name: &str) -> Result<Option<BranchRef>>

One local branch, read now: the same fields as branches, for a caller that must not act on a reading taken earlier. None when the branch no longer exists.

for-each-ref refs/heads/<name> also matches the branches below <name>/, so the result is filtered to the exact name.

use majordomus_cli::worktree::state::branch;
let repo = tempfile::tempdir().unwrap();
let git = |args: &[&str]| {
    let ok = std::process::Command::new("git")
        .args(["-c", "user.name=t", "-c", "user.email=t@t", "-c", "commit.gpgsign=false"])
        .args(args)
        .current_dir(repo.path())
        .status()
        .unwrap();
    assert!(ok.success(), "git {args:?}");
};
git(&["init", "-q", "-b", "trunk"]);
git(&["commit", "-q", "--allow-empty", "-m", "root"]);
git(&["branch", "feat/sub"]);

// `refs/heads/feat` matches feat/sub as well; the exact-name filter drops it.
assert!(branch(repo.path(), "feat").unwrap().is_none());
let feat = branch(repo.path(), "feat/sub").unwrap().expect("feat/sub exists");
assert_eq!(feat.name, "feat/sub");
assert!(feat.upstream.is_none());
assert_eq!(feat.head.len(), 40);
assert!(branch(repo.path(), "trunk").unwrap().unwrap().worktree.is_some());
assert!(branch(repo.path(), "gone").unwrap().is_none());