Use the release branch for sytest in release-branch PRs (#17306)

.github/workflows/tests.yml

@@ -479,6 +479,9 @@ jobs:
       volumes:
         - ${{ github.workspace }}:/src
       env:
+        # If this is a pull request to a release branch, use that branch as default branch for sytest, else use develop
+        # This works because the release script always create a branch on the sytest repo with the same name as the release branch
+        SYTEST_DEFAULT_BRANCH: ${{ startsWith(github.base_ref, 'release-') && github.base_ref || 'develop' }}
         SYTEST_BRANCH: ${{ github.head_ref }}
         POSTGRES: ${{ matrix.job.postgres && 1}}
         MULTI_POSTGRES: ${{ (matrix.job.postgres == 'multi-postgres') || '' }}

changelog.d/17306.misc

@@ -0,0 +1 @@
+Use the release branch for sytest in release-branch PRs.