Changelogs for Grunt

build.json

{
    "builds": {},
    "lastSince": null
}

Gruntfile.js

grunt.registerTask('changelog', 'Create git changelog', function () {
    var exec = require('child_process').exec;
    var path = require('path');

    var cmd;
    var d = new Date();
    var data = grunt.file.readJSON('build.json');
    var now = d.getFullYear() + '-' + (d.getMonth() + 1) + '-' + d.getDate();   // yyyy-mm-dd
    var since = grunt.option('since') || data.lastSince || now;
    var targetFile = path.normalize(__dirname + '/changelogs/changelog_since_' + since + '.txt');

    // save current date as the next target changelog startdate
    if (!data.lastSince || data.lastSince !== since) {
        data.lastSince = since;
        data.builds[new Date().toString()] = since;
        grunt.file.write('build.json', JSON.stringify(data, null, 4));
    }

    // create changelog
    cmd = 'git log --name-only --since=' + since + ' > ' + targetFile;
    exec(cmd);
});