let mut stream = FastExportStream {
        branch_name: matches.opt_str("b").unwrap_or(channel.to_string()),
    };

    let mut stream = FastExportStream::new(matches.opt_str("b").unwrap_or(channel.to_string()));

    for c in changes {
        stream.write_commit(&c);

    for i in 0..changes.len() {
        let parent = if i == 0 {
            None
        } else {
            Some(changes[i-1].state)
        };
        stream.write_commit(&changes[i], parent);

use std::collections::HashMap;

    max_commit_mark: i32,
    commit_marks: HashMap<libpijul::Merkle, i32>,

    pub fn write_commit(&mut self, c: &Change) {

    pub fn new(branch_name: String) -> FastExportStream {
        return FastExportStream {
            branch_name,
            max_commit_mark: 0,
            commit_marks: HashMap::new(),
        };
    }
    pub fn write_commit(&mut self, c: &Change, parent: Option<libpijul::Merkle>) {

        // TODO: mark

        let mark = self.commit_marks.entry(c.state).or_insert_with(|| {
            self.max_commit_mark += 1;
            self.max_commit_mark
        });
        println!("mark :{}", mark);

        // TODO: from

        match parent {
            Some(p) => {
                match self.commit_marks.get(&p) {
                    Some(p_mark) => println!("from :{}", p_mark),
                    None => {},
                }
            },
            None => {},
        }