Directly refer to GitHub events

instead of unnecessarily defining env vars

.github/workflows/macos.yml

@@ -27,12 +27,8 @@ jobs:
         if: github.event_name == 'push'
       - name: Checkout a pull request
         run: |
-          git clone --single-branch --shallow-since=yesterday "--branch=$GITHUB_BRANCH" "https://github.com/${GITHUB_REPO}" src
-          git -C src reset --hard "$GITHUB_REV"
-        env:
-          GITHUB_REV: ${{ github.event.pull_request.head.sha }}
-          GITHUB_BRANCH: ${{ github.event.pull_request.head.ref }}
-          GITHUB_REPO: ${{ github.event.pull_request.head.repo.full_name }}
+          git clone --single-branch --shallow-since=yesterday --branch=${{ github.event.pull_request.head.ref }} https://github.com/${{ github.event.pull_request.head.repo.full_name }} src
+          git -C src reset --hard ${{ github.event.pull_request.head.sha }}
         if: github.event_name == 'pull_request'
       - run: ./src/tool/actions-commit-info.sh
         id: commit_info

.github/workflows/mingw.yml

@@ -42,11 +42,10 @@ jobs:
           git clone --single-branch --shallow-since=yesterday https://github.com/ruby/ruby src
           git -C src reset --hard "$GITHUB_SHA"
         if: github.event_name == 'push'
-      # It's hard to propagate `env` to this workflow's shell environment to checkout PR. Using unstable actions/checkout as a workaround.
       - name: Checkout a pull request
-        uses: actions/checkout@v2
-        with:
-          path: src
+        run: |
+          git clone --single-branch --shallow-since=yesterday --branch=${{ github.event.pull_request.head.ref }} https://github.com/${{ github.event.pull_request.head.repo.full_name }} src
+          git -C src reset --hard ${{ github.event.pull_request.head.sha }}
         if: github.event_name == 'pull_request'
       - run: ./src/tool/actions-commit-info.sh
         shell: bash

.github/workflows/mjit.yml

@@ -29,12 +29,8 @@ jobs:
         if: github.event_name == 'push'
       - name: Checkout a pull request
         run: |
-          git clone --single-branch --shallow-since=yesterday "--branch=$GITHUB_BRANCH" "https://github.com/${GITHUB_REPO}" src
-          git -C src reset --hard "$GITHUB_REV"
-        env:
-          GITHUB_REV: ${{ github.event.pull_request.head.sha }}
-          GITHUB_BRANCH: ${{ github.event.pull_request.head.ref }}
-          GITHUB_REPO: ${{ github.event.pull_request.head.repo.full_name }}
+          git clone --single-branch --shallow-since=yesterday --branch=${{ github.event.pull_request.head.ref }} https://github.com/${{ github.event.pull_request.head.repo.full_name }} src
+          git -C src reset --hard ${{ github.event.pull_request.head.sha }}
         if: github.event_name == 'pull_request'
       - run: ./src/tool/actions-commit-info.sh
         id: commit_info

.github/workflows/ubuntu.yml

@@ -60,12 +60,8 @@ jobs:
         if: github.event_name == 'push'
       - name: Checkout a pull request
         run: |
-          git clone --single-branch --shallow-since=yesterday "--branch=$GITHUB_BRANCH" "https://github.com/${GITHUB_REPO}" src
-          git -C src reset --hard "$GITHUB_REV"
-        env:
-          GITHUB_REV: ${{ github.event.pull_request.head.sha }}
-          GITHUB_BRANCH: ${{ github.event.pull_request.head.ref }}
-          GITHUB_REPO: ${{ github.event.pull_request.head.repo.full_name }}
+          git clone --single-branch --shallow-since=yesterday --branch=${{ github.event.pull_request.head.ref }} https://github.com/${{ github.event.pull_request.head.repo.full_name }} src
+          git -C src reset --hard ${{ github.event.pull_request.head.sha }}
         if: github.event_name == 'pull_request'
       - run: ./src/tool/actions-commit-info.sh
         id: commit_info