use log::*;

                let mut txn = repo.pristine.mut_txn_begin()?;
                let channel_name = if let Some(ref c) = channel {

                let txn = repo.pristine.mut_txn_begin()?;
                let channel_name = if let Some(c) = channel {

                    txn.current_channel().unwrap_or(crate::DEFAULT_CHANNEL)

                    txn.current_channel()
                        .unwrap_or(crate::DEFAULT_CHANNEL)
                        .to_string()

                try_record(&mut repo, &channel_name)?;

                debug!("channel_name = {:?}", channel_name);
                let txn = Arc::new(RwLock::new(txn));
                try_record(&mut repo, txn.clone(), &channel_name)?;
                let mut txn = if let Ok(txn) = Arc::try_unwrap(txn) {
                    txn.into_inner().unwrap()
                } else {
                    unreachable!()
                };

fn try_record(repo: &mut Repository, channel: &str) -> Result<(), anyhow::Error> {
    let txn = repo.pristine.mut_txn_begin()?;
    if let Some(channel) = txn.load_channel(channel)? {
        let mut state = libpijul::RecordBuilder::new();
        state.record(
            Arc::new(RwLock::new(txn)),
            libpijul::Algorithm::default(),
            channel,
            repo.working_copy.clone(),
            &repo.changes,
            "",
            num_cpus::get(),
        )?;
        let rec = state.finish();
        if !rec.actions.is_empty() {
            bail!("Cannot change channel, as there are unrecorded changes.")
        }

fn try_record<T: ChannelMutTxnT + TxnT + Send + Sync + 'static>(
    repo: &mut Repository,
    txn: Arc<RwLock<T>>,
    channel: &str,
) -> Result<(), anyhow::Error> {
    let channel = if let Some(channel) = txn.read().unwrap().load_channel(channel)? {
        channel

    };
    let mut state = libpijul::RecordBuilder::new();
    state.record(
        txn,
        libpijul::Algorithm::default(),
        channel,
        repo.working_copy.clone(),
        &repo.changes,
        "",
        num_cpus::get(),
    )?;
    let rec = state.finish();
    if !rec.actions.is_empty() {
        bail!("Cannot change channel, as there are unrecorded changes.")

    debug!("restoring graph");

    let mut vi = Vec::new();
    for i in ::sanakirja::btree::iter(&filetxn, &external, None).unwrap() {
        debug!("{:?}", i);
        vi.push(i.unwrap());
    }
    vi.sort();
    debug!("restoring graph {:?}", vi);