How to rename an R package

I have written a package that I do not wish to change, but I now wish to write a slight variant of it. When that variant is working and if I like it, I may wish to merge it with the older package, but for now I just want to get the variant working to see if it is something I want to proceed with.

What I want to do is this:

  1. My existing package is package0.
  2. Copy package0 to new folder, so I now have two identical packages named package0 saved in different folders
  3. Rename the second as package1
  4. Amend package1

My problem is that renaming a package seems to require lots of individual text amendments in a variety of files.

Is there an easy way to rename a copy of a package?