If you are comfortable writing a Stash plugin there are events for when a PR is created/updated, which you can listen too and then update your CI system.
Some links which may help:
Quite possibly someone has already written something for your CI. Which CI server are you using?
Hello! My name is Mark Askew and I am a Premier Support Engineer for products Bitbucket Server/Data Center, Fisheye & Crucible. Today, I want to bring the discussion that Jennifer, Matt, and ...
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