<p><strong>What is the best way to make one of the branches of a subversion repository the new trunk?</strong>  </p>

<p>There has been a major rewrite for the entire system: things have been moved around, rewritten, replaces, removed, renamed etc. The rewritten code has been tested and is ready to replace the old trunk.</p>

<p>Basically, the the old mainline (Trunk 5) is tagged and will end here. The rewritten branch (Branch 6) is to become the new mainline (Trunk 7):</p>

<pre>
Trunk(1) --> Trunk(2) --> Trunk(5) --> &times;          +--> new Trunk(7)
  \                             \                 |
  fork                         merge             ???
    \                             \               |
     +--> Branch(3) --> Branch(4) --> Branch(6) --+
</pre>

<p>All ongoing changes from the old 'Trunk' are already incorporated in the 'Rewritten branch'</p>

<p><strong>How can I do this?</strong></p>

Use
svn move
to move the contents of the old trunk somewhere else and rename the branch to trunk afterward.
Note that copy and move in svn work like file operations. You can use them to move/copy stuff around in your repository and these changes are versioned as well. Think of "move" as "copy+delete".
[EDIT] Nilbus just notified me that you will get merge conflicts when you use
```
svn move
```
.
I still think that this is the correct approach. It will cause conflicts but if you merge carefully, chances are that you won't lose any data. If that bothers you, use a better VCS like
Mercurial
or
Git
.