Function try_parse_double_dot_log_range 

pub fn try_parse_double_dot_log_range(
    repo: &Repository,
    spec: &str,
) -> Result<Option<(ObjectId, ObjectId)>>

When spec uses two-dot range syntax (A..B, ..B, A..), returns the commits to exclude (left tip) and include (right tip) for git log-style walks.

Returns Ok(None) when spec is not a two-dot range. Symmetric A...B is handled by resolve_revision_as_commit instead.

Errors

Propagates resolution errors from either range endpoint.