What does "--svn-branches" do exactly?

[achimmihca]

When running the tool without parameters, it shows
--svn-branches Use the contents of SVN when creating branches, Note: SVN tags are branches as well

But this does not make sense to me.
The tool always uses the contents of SVN when creating branches, does it not?

What is the difference to not using this option?

[nickwilliams-zaxiom]

I would also like to know the answer to this question. No documentation says anything other than that ^^, but yet nearly every example I can find anywhere uses --svn-branches. I even read the source code, hoping I could gleam an answer, but I just don't understand enough about how the code works to figure it out.