Function format_git_time 

pub fn format_git_time(seconds: i64, offset_minutes: i32) -> String

Format a Unix timestamp (+ minute offset) as YYYY-MM-DD HH:MM:SS ±HHMM in the given timezone, with no external date crate. Uses Howard Hinnant’s civil-from-days algorithm so it is correct for the full proleptic Gregorian range.