Fixes git workspace after checking out benchmarks

With the introduction of composite actions in the GitHub workflows,
the ci-perf.yml workflow broke.

This happens because the setup-action configures a Post Run (a hook
to be executed after the workflow).

Since the benchmarks checkout a different orphan branch, when that
Post Run executes, it cannot find the action anymore.

To fix it, I introduce a new step that restores the git workspace,
making it available for that hook.

Author: alganet

.github/workflows/ci-perf.yml

@@ -77,3 +77,12 @@ jobs:
           git add .phpbench latest.md
           git commit -m "Store benchmark results [skip ci]" || echo "No changes to commit"
           git push origin benchmarks
+
+      - name: Restore workspace
+        if: always()
+        run: |
+          set -euo pipefail
+          echo "Restoring workspace to original commit: ${GITHUB_SHA}"
+          git fetch origin || true
+          git checkout --detach "${GITHUB_SHA}"
+          git reset --hard "${GITHUB_SHA}"