function _setDocInfo(doc) {
        // FUTURE: some of these things should just be moved into core Document; others should
        // be in a LiveDevelopment-specific object attached to the doc.
        var matches = /^(.*\/)(.+\.([^.]+))$/.exec(doc.file.fullPath);
        if (matches) {
            var prefix = "file://";

            // The file.fullPath on Windows starts with a drive letter ("C:").
            // In order to make it a valid file: URL we need to add an 
            // additional slash to the prefix.
            if (brackets.platform === "win") {
                prefix += "/";
            }

            doc.extension = matches[3];
            doc.url = encodeURI(prefix + doc.file.fullPath);

            // the root represents the document that should be displayed in the browser
            // for live development (the file for HTML files, index.html for others)
            var fileName = /^html?$/.test(matches[3]) ? matches[2] : "index.html";
            doc.root = {url: encodeURI(prefix + matches[1] + fileName)};
        }
    }
Augments the given Brackets document with information that's useful for live development.