I have a Jenkins job that performs polling of an SVN trunk and launches a complex chain of jobs if the trunk was updated.

What I'd like to do is to give users the ability to launch the job manually, specifying a different branch to checkout - e.g., to test the code in a branch before merging it to the trunk. Currently, I can do the following:

• Set the Repository URL to https://svn/$BRANCH
• Set the default value of parameter BRANCH to trunk/xyz
• Let users type in the branch, OR use the List Subversion Tags option

However, this does not work as expected – or maybe I have misinterpreted the behavior, in which case please correct me.
The way I understand it, such configuration works like this:
0) I set up the job as described above
1) The job is polling the trunk, since this is the default value of the parameter
2) I launch the job manually, choosing a different branch to checkout. It runs successfully
3) After that, the job begins to poll the branch instead of the trunk. This is absolutely not what I expect it to do – manual launches should not interfere with future automatic polling.

I understand this is the way Jenkins works with parameters, so I am filing this as a feature request.