How to update files without overwriting

I'm trying to figure out a way to update several text files with new content WITHOUT replacing the original files. Essentially, the files exist on a shared webdav (network drive), and the software reading the files has created generic "permanent links" to the files.

I have copied all of the files (about 600 of them) off the webdav onto my computer and painstakingly updated each and every one of them. But when I copy them back onto the webdav, it breaks the permanent links. Is there any way to do an "update" copy instead of a "replace" copy in os x? That way, the file doesn't get deleted and replaced, and instead just updates the contents of the files?

Thanks for any help you can give!