1. A method of maintaining synchronism of a computer file at a first computer, said method comprising: providing a first version of said computer file from said first computer to a second computer; modifying at said second computer said first version of said computer file to create a second version of said computer file; maintaining a first change log at said second computer, reflecting changes resulting from said modifying at said second computer; sending said second version of said computer file and said first change log from said second computer to a third computer without sending said first change log to said first computer; at said third computer, receiving said second version of said computer file, and entries of said first change log from said second computer, to permit said second version of said computer file to be modified at said third computer, and to allow said third computer to relay said first change log to another computer; modifying at said third computer, said second version of said computer file, to create a third version of said computer file; maintaining a second change log at said third computer, reflecting changes resulting from said modifying at said third computer; and at said first computer, receiving, from said third computer, entries of said first change log received at said third computer, and entries of said second change log, and synchronizing said computer file at said first computer with said second and third versions of said computer file using received entries of said first change log and said second change log, thereby applying changes in said second version of said computer file and said third version of said computer file to said computer file at said first computer.