Simplify prerelease action merge commit detection.

.github/workflows/tests.yml

@@ -251,40 +251,40 @@ jobs:
       - uses: actions/checkout@v4
         with:
           fetch-depth: 0
-      # asking github if something was not a merge commit is surprisingly difficult
-      - run: git rev-parse HEAD^2 2>/dev/null >/dev/null || echo NOT_MERGE_COMMIT=1 | tee -a $GITHUB_ENV
+      # asking github if something was a merge commit is surprisingly difficult
+      - run: git rev-parse HEAD^2 2>/dev/null >/dev/null && echo MERGE_COMMIT=1 | tee -a $GITHUB_ENV || true
       - name: Set up Python
-        if: ${{ env.NOT_MERGE_COMMIT == '' }}
+        if: env.MERGE_COMMIT
         uses: actions/setup-python@v5
         with:
           python-version: "3.x"
       - name: Set Node.js 20.x
-        if: ${{ env.NOT_MERGE_COMMIT == '' }}
+        if: env.MERGE_COMMIT
         uses: actions/setup-node@v4
         with:
           node-version: 20.x
       - name: Install Yarn
-        if: ${{ env.NOT_MERGE_COMMIT == '' }}
+        if: env.MERGE_COMMIT
         run: npm install -g yarn
       - name: Install dependencies
-        if: ${{ env.NOT_MERGE_COMMIT == '' }}
+        if: env.MERGE_COMMIT
         run: |
           python -m pip install --upgrade pip poetry
           python -m poetry config virtualenvs.create false
           python -m poetry self add "poetry-dynamic-versioning[plugin]"
       # Pre-build the UI bundle and don't repeat it on the build step to allow sdist to find the files
       - name: Prebuild UI
-        if: ${{ env.NOT_MERGE_COMMIT == '' }}
+        if: env.MERGE_COMMIT
         run: |
           yarn webui:install
           yarn webui:build
       - name: Build
-        if: ${{ env.NOT_MERGE_COMMIT == '' }}
+        if: env.MERGE_COMMIT
         run: |
           SKIP_PRE_BUILD=true python -m poetry build
           ./rename-wheel.sh
       - name: Publish prerelease version to PyPI
-        if: ${{ env.NOT_MERGE_COMMIT == '' }}
+        if: env.MERGE_COMMIT
         uses: pypa/gh-action-pypi-publish@release/v1
         with:
           user: __token__