`git push` automatically closes my `arc diff`

I'm stuck on a problem where pushing my code to a remote branch automatically closes my diffs. An example:

• I have a diff, say DXXXXXX
• I want to take all the changes in that diff push them to a new branch, say test-branch
• After running git push origin +test-branch:test-branch, Phabricator closes DXXXXXX

Why does this happen? How can I decouple my diff away from pushing code to a new branch?

I tried to create a brand new git history, so that the test-branch commits have no overlap with the Diff, but that didn't work. Somehow Phabricator still associates the 'new commits' with the old diff :(