slate.js

var ST_APP_NAME = 'SourceTree';
var resize = function(windowObject, opt) {
    opt = opt || {};
    opt.style = "bar-resize:screenSizeX * .6";

    var ST_BOOKMARKS_WIDTH = 500;

    switch (windowObject.app().name()) {
        case ST_APP_NAME:
            opt.style = "bar-resize:screenSizeX - " + ST_BOOKMARKS_WIDTH;

            switch (windowObject.title()) {
                case ST_APP_NAME:
                    //ST bookmarks window
                    opt.style = 'bar-resize: ' + ST_BOOKMARKS_WIDTH;
                    opt.direction = opt.direction || 'right';
                    break;
            }

            opt.direction = opt.direction || 'left';
            break;
    }

    var opRet = windowObject.doOperation(slate.operation("push", opt));
    if (0) {
        S.log('[' + windowObject.title() + ']' +
                '[' + windowObject.app().name() + ']' +
                JSON.stringify(opt) +
                ' - returned ' + opRet);

    }
};

slate.bindAll({
    "f:cmd,alt": slate.op("move", {"x": "screenOriginX", "y": "screenOriginY",
        "width": "screenSizeX", "height": "screenSizeY"}),
    "left:cmd,alt": function(windowObject) {
        resize(windowObject, {direction: 'left'});
    },
    "right:cmd,alt": function(windowObject) {
        resize(windowObject, {direction: 'right'});
    },
    "right:cmd,ctrl,alt": slate.op("throw", {"screen": "right", "style":
        "bar-resize:screenSizeX * .6"}),
    "left:cmd,ctrl,alt": slate.op("throw", {"screen": "left", "style":
        "bar-resize:screenSizeX * .6"})
});

var startupRetile = function(windowObject) {
    switch (windowObject.app().name()) {
        case ST_APP_NAME:
            resize(windowObject);
            break;
    }
}

slate.on("windowOpened", function(ev, windowObject){
    startupRetile(windowObject);
});
slate.on("appOpened", function(ev, app){
    app.eachWindow(function(windowObject){
        startupRetile(windowObject);
    });
});