Try basing release notes on github.sha rather than github.ref_name.

Author: nat-goodspeed

.github/workflows/build.yaml

@@ -382,7 +382,7 @@ jobs:
             ${{ needs.build.outputs.relnotes }}
           prerelease: true
           generate_release_notes: true
-          target_commitish: ${{ github.ref_name }}
+          target_commitish: ${{ github.sha }}
           append_body: true
           fail_on_unmatched_files: true
           files: |