Function resolve_root 

pub fn resolve_root(
    source: &mut impl ObjectSource,
    id: ObjectId,
    max_tags: u32,
) -> Result<Root>

Peel at most max_tags annotated tags, check each declared target’s actual type and format, then resolve a commit’s tree (or a direct tree/blob ref). A tag cycle exhausts the explicit bound. No recursion or allocation is used.