Add CI workflow to check c10 is synced with PyTorch (#10413)

This script checks that all files in our c10 copy are in sync with our
pinned version of PyTorch.

Test Plan: 1) detected us being out of sync when I wrote this PR
2) CI to run it and make sure that we are clean now

Author: swolchok

.ci/scripts/check_c10_sync.sh

@@ -0,0 +1,14 @@
+#!/bin/bash
+# Copyright (c) Meta Platforms, Inc. and affiliates.
+# All rights reserved.
+#
+# This source code is licensed under the BSD-style license found in the
+# LICENSE file in the root directory of this source tree.
+
+set -eux
+ls pytorch/.git || git clone https://github.com/pytorch/pytorch.git
+pytorch_pin="$(< .ci/docker/ci_commit_pins/pytorch.txt)"
+pushd pytorch
+git checkout "$pytorch_pin"
+popd
+"$(dirname "${BASH_SOURCE[0]}")"/compare_dirs.sh runtime/core/portable_type/c10/c10 pytorch/c10

.ci/scripts/compare_dirs.sh

@@ -0,0 +1,54 @@
+#!/bin/bash
+# Copyright (c) Meta Platforms, Inc. and affiliates.
+# All rights reserved.
+#
+# This source code is licensed under the BSD-style license found in the
+# LICENSE file in the root directory of this source tree.
+
+set -eux
+
+# Check if dir1's files are also found in dir2 with the same
+# contents. Exempt files named BUCK, CMakeLists.txt, TARGETS, or
+# targets.bzl.
+
+if [ $# -ne 2 ]; then
+    echo "Usage: $0 dir1 dir2" >&2
+    exit 1
+fi
+dir1="$1"
+dir2="$2"
+
+if [ ! -d "$dir1" ] || [ ! -d "$dir2" ]; then
+    echo "Error: Both directories must exist" >&2
+    exit 1
+fi
+
+exit_status=0
+while IFS= read -r -d '' file; do
+    base=$(basename "$file")
+    case "$base" in
+        "BUCK"|"CMakeLists.txt"|"TARGETS"|"targets.bzl")
+            continue
+            ;;
+    esac
+    # Construct the corresponding path in the second directory
+    file2="$dir2/${file#$dir1/}"
+    # Check if the corresponding file exists in the second directory
+    if [ ! -f "$file2" ]; then
+        echo "Error: File '$file' found in '$dir1' but not found in '$dir2'" >&2
+        exit 1
+    fi
+    # Compare the contents of the two files using diff
+    set +ex
+    differences=$(diff -u -p "$file" "$file2")
+    set -e # leave x off
+    # If there are any differences, print an error message and exit with failure status
+    if [ -n "$differences" ]; then
+        echo "Error: Mismatch detected in file '$file':" >&2
+        echo "$differences" >&2
+        exit_status=1
+    fi
+    set -x
+done < <(find "$dir1" -type f -print0)
+
+exit $exit_status

.github/workflows/check-c10-sync.yml

@@ -0,0 +1,27 @@
+name: check-c10-sync
+
+on:
+  pull_request:
+    paths:
+      - .ci/docker/ci_commit_pins/pytorch.txt
+      - .ci/scripts/compare_dirs.sh
+      - runtime/core/portable_type/c10/**
+
+concurrency:
+  group: ${{ github.workflow }}-${{ github.event.pull_request.number || github.sha }}-${{ github.event_name == 'workflow_dispatch' }}-${{ github.event_name == 'schedule' }}
+  cancel-in-progress: true
+
+jobs:
+  check-c10-sync:
+    permissions:
+      id-token: write
+      contents: read
+    name: check-c10-sync
+    runs-on: ubuntu-latest
+    steps:
+      - uses: actions/checkout@v3
+        with:
+          fetch-depth: 0
+      - name: Clone PyTorch
+        run: |
+          .ci/scripts/check_c10_sync.sh