[svn] Svn switch from trunk to branch

I am in the root folder of an SVN-hosted project's trunk and am exploring setting up two branches.

One branch will be a "snapshot" of the project at the current (stable) revision, and a second branch will be one I'll work on to apply some new code, test, and then upgrade the trunk to a new version.

My goal is to keep the snapshot as insurance and a quick way to get an older, stable version of our project. The second branch, once we apply fresh code and the tests pass, will be merged back into the trunk, which we offer to the public.

To set up the snapshot, I copied our trunk to a branch called v1p2p3:

$ svn cp https://www.example.com/svn/trunk \ 
         https://www.example.com/svn/branches/v1p2p3 \
         -m "Branching from root trunk to v1p2p3 at r1114"

So far, so good:

Committed revision 1115.

What I would like to do is switch my local repository copy to this branch, to make sure that things worked, but I get an error message:

$ svn switch --relocate https://www.example.com/svn/trunk \
                        https://www.example.com/svn/branches/v1p2p3

The error message is:

svn: E155024: Invalid relocation destination: 
              'https://www.example.com/svn/branches/v1p2p3' 
              (does not point to target)

What am I doing wrong?

(If this doesn't work, I suspect I can't get to starting on the more ambitious second branch. I'm looking for a way to do this that won't damage the existing project layout. Thanks for your advice, and apologies if this is a dumb question.)

In my case, I wanted to check out a new branch that has cut recently but it's it big in size and I want to save time and internet bandwidth, as I'm in a slow metered network

so I copped the previous branch that I already checked in

I went to the working directory, and from svn info, I can see it's on the previous branch I did the following command (you can find this command from svn switch --help)

svn switch ^/branches/newBranchName

go check svn info again you can see it is becoming the newBranchName go ahead and svn up

and this how I got the new branch easily, quickly with minimum data transmitting over the internet

hope sharing my case helps and speeds up your work

• Short version of (correct) tzaman answer will be (for fresh SVN)

  svn switch ^/branches/v1p2p3
  

• --relocate switch is deprecated anyway, when it needed you'll have to use svn relocate command

• Instead of creating snapshot-branch (ReadOnly) you can use tags (conventional RO labels for history)

On Windows, the caret character (^) must be escaped:

svn switch ^^/branches/v1p2p3