reinstate doc upload (#7580)

Author: pmeier

.github/workflows/docs.yml

@@ -7,13 +7,17 @@ on:
       - nightly
       - main
       - release/*
+    tags:
+      - v[0-9]+.[0-9]+.[0-9]
+      - v[0-9]+.[0-9]+.[0-9]+-rc[0-9]+
   workflow_dispatch:
 
 jobs:
   build:
     uses: pytorch/test-infra/.github/workflows/linux_job.yml@main
     with:
       repository: pytorch/vision
+      upload-artifact: docs
       script: |
         set -euo pipefail
 
@@ -44,4 +48,60 @@ jobs:
         sed -i -e 's/-j auto/-j 1/' Makefile
         make html
         
-        mv build/html/* "${RUNNER_DOCS_DIR}"
+        cp -r build/html "${RUNNER_ARTIFACT_DIR}"
+        
+        # On PRs we also want to upload the docs into our S3 bucket for preview.
+        if [[ ${{ github.event_name == 'pull_request' }} ]]; then
+          cp -r build/html/* "${RUNNER_DOCS_DIR}"
+        fi
+
+  upload:
+    needs: build
+    if: github.repository == 'pytorch/vision' && github.event_name == 'push' && 
+        ((github.ref_type == 'branch' && github.ref_name == 'main') || github.ref_type == 'tag')
+    permissions:
+      contents: write
+    uses: pytorch/test-infra/.github/workflows/linux_job.yml@main
+    with:
+      repository: pytorch/vision
+      download-artifact: docs
+      ref: gh-pages
+      script: |
+        set -euo pipefail
+        
+        REF_TYPE=${{ github.ref_type }}
+        REF_NAME=${{ github.ref_name }}
+
+        if [[ "${REF_TYPE}" == branch ]]; then
+          TARGET_FOLDER="${REF_NAME}"
+        elif [[ "${REF_TYPE}" == tag ]]; then
+          case "${REF_NAME}" in
+            *-rc*)
+              echo "Aborting upload since this is an RC tag: ${REF_NAME}"
+              exit 0
+              ;;
+            *)
+              # Strip the leading "v" as well as the trailing patch version. For example:
+              # 'v0.15.2' -> '0.15'
+              TARGET_FOLDER=$(echo "${REF_NAME}" | sed 's/v\([0-9]\+\)\.\([0-9]\+\)\.[0-9]\+/\1.\2/')
+              ;;
+          esac
+        fi
+        echo "Target Folder: ${TARGET_FOLDER}"
+
+        mkdir -p "${TARGET_FOLDER}"
+        rm -rf "${TARGET_FOLDER}"/*
+        mv "${RUNNER_ARTIFACT_DIR}"/html/* "${TARGET_FOLDER}"
+        git add "${TARGET_FOLDER}" || true
+        
+        if [[ "${TARGET_FOLDER}" == main ]]; then
+          mkdir -p _static
+          rm -rf _static/*
+          cp -r "${TARGET_FOLDER}"/_static/* _static
+          git add _static || true
+        fi
+        
+        git config user.name 'pytorchbot'
+        git config user.email '[email protected]'
+        git commit -m "auto-generating sphinx docs" || true
+        git push