Function upstream 

pub async fn upstream(branch: impl AsRef<OsStr>) -> Option<String>

Returns the qualified name of the remote branch being tracked by the specified tracking branch, or None if the branch is not a tracking branch.

Examples

Assuming the local main branch is tracking origin/main:

use grit::git;

async fn assert_main() {
    assert_eq!(git::upstream("main").await.as_deref(), Some("origin/main"));
}