shaHistory.js

    const shaHistory$ = O.create(o => {
        const getNext = () => {
            revwalk.next()
                .then(value => {
                    if (value) {
                        o.onNext(value);
                        getNext();
                    } else {
                        o.onCompleted();
                    }
                })
                .catch(err => {
                  if (err.errno !== Git.Error.CODE.ITEROVER) {
                    o.onError(err);
                  } else {
                    o.onCompleted();
                  }
                });
        };

        getNext();
    });