function applyIndentationDiff(code, diff, indentChar, includeEmptyLines) {
    var lines = getLineData(code);
    for (var i = 1; i < lines.length; i++) {
        var lineData = lines[i];
        var currentIndent;
        if (lineData.line.length === 0 && i !== lines.length - 1 && !includeEmptyLines) {
            continue;
        }
        var match = NON_WHITESPACE.exec(lineData.line);
        if (match) {
            currentIndent = match.index;
        } else {
            currentIndent = lineData.line.length;
        }
        lineData.line = new Array(Math.max(currentIndent + diff, 0) + 1).join(indentChar) +
            lineData.line.slice(currentIndent);
    }
    return convertLinesToString(lines);
}
Applies indentation diff.

@param {String} code
@param {Number} diff
@param {String} indentChar
@param {Boolean} includeEmptyLines