chore(ci): Try to push to PR head

Author: effigies

.github/workflows/pixi-lock.yml

@@ -18,6 +18,26 @@ jobs:
         with:
           ref: ${{ github.event.pull_request.head.sha }}
           token: ${{ secrets.GITHUB_TOKEN }}
+      - name: Dump GitHub context
+        env:
+          GITHUB_CONTEXT: ${{ toJson(github) }}
+        run: |
+          echo "$GITHUB_CONTEXT"
+      - name: Find submitting repository
+        id: get-source-repo
+        uses: actions/github-script@v8
+        env:
+          OWNER: ${{ github.repository_owner }}
+          REPO: ${{ github.repository }}
+          PULL: ${{ github.event.number }}
+        with:
+          script: |
+            const { data } = await github.rest.pulls.get({
+              owner: process.env.OWNER,
+              repo: process.env.REPO.split('/')[1],
+              pull_number: process.env.PULL,
+            });
+            core.setOutput('remote', data.head.repo.html_url)
       - name: Set git identity
         run: |
           git config --global user.name "nipreps[bot]"
@@ -32,4 +52,8 @@ jobs:
         run: |
           uvx datalad run -i pixi.lock -i pyproject.toml -o pixi.lock -- pixi lock
       - name: Push updated lockfile, if needed
-        run: git push
+        run: |
+          git push $REMOTE HEAD:refs/pull/$PULL/head
+        env:
+          REMOTE: ${{ steps.get-source-repo.outputs.remote }}
+          PULL: ${{ github.event.number }}