Function commit_object_is_signed 

pub fn commit_object_is_signed(commit_content: &str) -> bool

Whether a raw git commit object carries an SSH signature at all.

This is the same gpgsig SSH-block detection extract_ssh_signature uses to decide a commit is unsigned, exposed as a cheap predicate so callers that only need “did a signature land?” (e.g. confirming an amend actually signed) share the verifier’s single source of truth instead of re-grepping the object.