Final changes necessary to auto-update PyTorch version (#1438)

* build: push directly from CI to main branch

This avoids the need to create, approve, and merge a separate PR, in
addition to avoiding unnecessary CI runs for the PyTorch version update.

* build: schedule cronjob to run RollPyTorch action

This patch schedules the RollPyTorch action to be run at noon UTC, which
roughly corresponds to 4am Pacific Time.  We pick this time since the
commit for PyTorch nightly releases are picked just after midnight
Pacific Time and the nightly release artifacts are produced in about 2
to 3 hours after the commit is picked.

.github/workflows/RollPyTorch.yml

@@ -1,20 +1,27 @@
 name: Roll PyTorch
 
-on: workflow_dispatch
+on:
+  schedule:
+    - cron: '0 12 * * *'
+  workflow_dispatch:
 
 jobs:
   build_linux:
     name: Manylinux Build
     runs-on: ubuntu-latest
     steps:
+
     - name: Get torch-mlir
-      uses: actions/checkout@v2
+      uses: actions/checkout@v3
       with:
         submodules: 'true'
+        token: ${{ secrets.WORKFLOW_INVOCATION_TOKEN }}
+
     - name: Setup ccache
       uses: ./.github/actions/setup-build
       with:
         cache-suffix: x86_64-out-of-tree-OFF
+
     - name: Determine nightly PyTorch version
       run: |
         cd ${GITHUB_WORKSPACE}
@@ -33,6 +40,7 @@ jobs:
         # retrieve them when creating a PR
         echo "PT_HASH=${PT_HASH}" >> ${GITHUB_ENV}
         echo "PT_RELEASE=${PT_RELEASE}" >> ${GITHUB_ENV}
+
     - name: Build and test
       run: |
         cd ${GITHUB_WORKSPACE}
@@ -40,22 +48,14 @@ jobs:
         TORCH_MLIR_SRC_PYTORCH_BRANCH="${{ env.PT_HASH }}" \
         TORCH_MLIR_SRC_PYTORCH_RELEASE="${{ env.PT_RELEASE }}" \
         ./build_tools/python_deploy/build_linux_packages.sh
-    - name: Create PR to push new PyTorch version
-      uses: peter-evans/create-pull-request@v4
-      with:
-        token: ${{ secrets.WORKFLOW_INVOCATION_TOKEN }}
-        add-paths: |
-          pytorch-version.txt
-          pytorch-requirements.txt
-        delete-branch: true
-        branch: ${{ env.BRANCH }}
-        title: ${{ env.TITLE }}
-        author: Roll PyTorch Action <torch-mlir@users.noreply.github.com>
-        body: |
-          PyTorch commit hash `${{ env.PT_HASH }}`
-          ${{ github.server_url }}/${{ github.repository }}/actions/runs/${{ github.run_id }}
-        commit-message: |
-          ${{ env.TITLE }}
 
-          PyTorch commit hash `${{ env.PT_HASH }}`
-        reviewers: powderluv
+    - name: Push changes to main branch
+      run: |
+        cd ${GITHUB_WORKSPACE}
+        git config user.email "torch-mlir@users.noreply.github.com"
+        git config user.name "Roll PyTorch Action"
+        git fetch
+        git checkout main
+        git add pytorch-version.txt pytorch-requirements.txt
+        git commit -m "update PyTorch version to ${{ env.PT_RELEASE }}"
+        git push --set-upstream origin main