dart script for getting git info

git.dart

import 'dart:io';
import 'dart:async';

void main() {
  //getCurrentBranch(r'C:\Users\wgi7748\Desktop\noBS').then((output) => print(output));
  getHistory(r'C:\Users\wgi7748\Desktop\noBS', 3).then((entries) {
    assert(entries.length == 3);
    entries.forEach((e)
      => print('${e.author}: ${e.commitMessage} (${e.date})'));
  });
}

Future<List<GitHistoryEntry>> getHistory(String directory, int limit){
  final completer = new Completer<List<GitHistoryEntry>>();
  _executeGitCommand(directory, ['log', '-n', '$limit']).then((output){
    final ret = new List<GitHistoryEntry>();
    final lines = output.split('\n');
    assert(lines.length % 6 == 0);
    for(var i = 0; i < lines.length; i += 6){
      final logEntry = lines.skip(i).take(6).toList();
      final commitId = logEntry[0].substring(8);
      final author = logEntry[1].substring(8);
      final date = logEntry[2].substring(8);
      final message = logEntry[4].substring(4);
      final entry = new GitHistoryEntry(commitId, author, date, message);
      ret.add(entry);
    }
    completer.complete(ret);
  }, onError: (e) => completer.completeError(e));
  return completer.future;
}

Future<String> getCurrentBranch(String directory){
  final completer = new Completer<String>();
  _executeGitCommand(directory, ['branch']).then((String output){
    final branch = output.split('\n').firstWhere((String e) => e.startsWith('*'))
        .substring(2);
    completer.complete(branch);
  }, onError: (e) => completer.completeError(e));
  return completer.future;
}

Future<String> _executeGitCommand(String workingDirectory, List<String> args) {
  final completer = new Completer<String>();
  Process.start('git', args, workingDirectory: workingDirectory).then((process) {
    final buf = new StringBuffer();
    final stdInCompleter = new Completer();
    final stdErrCompleter = new Completer();
    final stdInComplete = stdInCompleter.future;
    final stdErrComplete = stdErrCompleter.future;
    process.stdout.listen((chars) => chars.forEach((char) => buf.writeCharCode(char)),
      onDone: () => stdInCompleter.complete(), onError: (e) => stdInCompleter.completeError(e));
    process.stderr.listen((chars) => chars.forEach((char) => buf.writeCharCode(char)),
      onDone: () => stdErrCompleter.complete(), onError: (e) => stdErrCompleter.completeError(e));

    process.exitCode.then((exitCode) {
      Future.wait([stdInComplete, stdErrComplete]).then((_) {
        if (exitCode == 0) {
          completer.complete(buf.toString());
        } else {
          completer.completeError(buf.toString());
        }
      });
    });
  });
  return completer.future;
}

class GitHistoryEntry {
  final String commitId;
  final String author;
  final String date;
  final String commitMessage;

  GitHistoryEntry(this.commitId, this.author, this.date, this.commitMessage);
}