Currently I'm working on a "plugin" that will be installed on many different sites and I was wondering on the best way for me to maintain the file version of this "plugin".

Here's what I was thinking. Have a "master copy" of the plugin on a server, then connect via FTP to the target sites and upload the copy to their site overwriting whatever files they may have.

I was wondering the best way to go about this.

The "plugin" will have many different folders and files so transferring one file at a time will be too tedious. Is there a way to copy an entire folder over at a time?

Or even better, is there a way to recurse through the folders and checking for file difference before uploading the new file? This is to make sure we are uploading a new file and not just the same one.