If you really want to keep the history intact, you can use svn cp to create a copy, which is then edited separately.
But I have never done this, and I donโt think I will ever be. The only reason I will do something like this would be for a file that is completely broken into parts, and not a method that moves from one file to another.
Instead, I would use a meaningful control comment: something like "foo created by extracting a bar from baz"
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