1. A computer-implemented method in a client computing system for synchronizing content of a file with a distinct and separate server computing system using a local data content index, the local data content index residing on the client computing system and indexing the data content of a plurality of files of the client computing system, comprising: determining one or more portions of the file; by performing an index lookup into the local data content index, and without querying the server computing system to find out what data content is already present on the server computing system, determining which of the determined one or more portions of the file correspond to data content deemed to be already present on the server computing system; generating a patch comprising one or more segments that correspond to the determined one or more portions of the file, each segment either containing data content or a reference to data content, the segment containing data content when the corresponding portion of the file is determined to correspond to data content not deemed to be already present on the server computing system, the segment containing a reference to data content when the corresponding portion of the file is determined to correspond to data content deemed to be already present on the server computing system; and forwarding the generated patch and causing the file to be generated on the server computing system from the patch in conjunction with data content already present on the server computing system, thereby synchronizing the content of the file without forwarding the entire data content of the file.