Function parse_trailer_command_line_arg 

pub fn parse_trailer_command_line_arg(
    raw: &str,
) -> Result<(String, String), TrailerArgParseError>

Split a git commit --trailer argument into token and value.

The separator is the first : or = in the string (whichever comes first), matching Git’s parse_trailer_arg / git interpret-trailers --trailer.

Errors

Returns TrailerArgParseError when neither separator appears.