Function prepare_commit_bytes 

pub fn prepare_commit_bytes(
    repo: &Repository,
    config: &ConfigSet,
    data: &CommitData,
    sign_override: Option<bool>,
) -> Result<Vec<u8>>

Serialize data and sign the bytes when should_sign_commit says so.

Does not assign change ids. Callers that need a change-id header (for example create_commit) set it with crate::change_id::set_change_id first. Stash, notes, and other auxiliary commits use this path without adding ids.

Errors

Propagates signing and config errors from GpgConfig::from_config and sign_serialized_commit.