I want to delete a svn branch to make sure people don't work on a archived branch by mistake (we have already merged the branch into the trunk).
However, I don't want to loose the branch's history and would ideally still want to be able to see the branch in tortoise svn's graph.
Can I have the best of both world (cleaned up branch's and history)?
As explained by others, you have to find the commit ID where the branch was deleted. Once you have the commit ID, you can use:
svn log -l 10 http://svn.exemple.com/svn/myapp/branches/1.0.0@42983
Search the commit ID where the release was created, assuming you know the tag name and you know that tag wasn't updated later:
svn log --stop-on-copy --limit 1 -r0:HEAD http://svn.exemple.com/svn/myapp/tags/1.0.0
Alternatively, you can search for the commit ID where that branch was deleted (a string like "D /branches/1.0.0") :
svn log --search branches/7.0.0 http://svn.exemple.com/svn/myapp/branches/ -v | grep -e 'D /branches/1.0.0' -e '^r.*' | grep "D " -B1| head -n 20