title: How to push modified code in a perforce changelist to another branch?
body: <p>Basically, I've got main and UnityVersion_Testing branches.  The team is all using p4v, but it's an uphill battle.  Our project is on an older version of Unity, and I'd like to run the automatic upgrade by running the old project in the new engine and then push to a branch we've got in Perforce specifically for such an occasion.</p>
  <p>What I thought I was supposed to do was run the upgrade, those files that are modified are now in a new pending changelist, I shelve those files, switch streams to UnityVersion_Testing, and then I thought I'd be able to unshelve those files there.  No luck.  The shelved files appear to belong to the other workspace.  I then tried to unshelve the files.  I can't, because they're still checked out, and I can't seem to get them into a state where they'll accept being unshelved.</p>
  <p>How do I pull latest from main, upgrade the assets in place in the new version of Unity, and then push to our existing UnityVersion_Testing branch so that I'm in a good place to merge those changes back into main when it's passed regression testing?</p>