Deploy documentation from GHA (#3292)

Summary: Pull Request resolved: https://github.com/pytorch/audio/pull/3292

Reviewed By: nateanl

Differential Revision: D45492729

Pulled By: mthrok

fbshipit-source-id: 11578166854c01deb50a6011550a91b87b426385

.github/workflows/build_docs.yml

@@ -7,21 +7,12 @@ 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:
-  upload:
-    runs-on: ubuntu-latest
-    needs: build
-    steps:
-    - uses: actions/download-artifact@v3
-      with:
-        name: docs
-    - name: Tweak the doc artifact
-      run: |
-        ls .
-
-    
   build:
     strategy:
       matrix:
@@ -86,3 +77,37 @@ jobs:
         (cd docs && make html)
 
         mv docs/build/html /artifacts/
+
+  commit:
+    if: github.repository == 'pytorch/audio'
+    permissions:
+      # Required for `git push`
+      # Note:
+      #   This is not effective from fork.
+      #   When you debug this, make sure to make a branch on pytorch and
+      #   make PR from there.
+      contents: write
+    runs-on: ubuntu-latest
+    needs: build
+    steps:
+    - uses: actions/checkout@v3
+      with:
+        ref: gh-pages
+    - uses: actions/download-artifact@v3
+      with:
+        name: docs
+    - name: Update nightly doc
+      # TODO: add tag-based process (need to handle the main directory name)
+      if: github.ref_name == 'nightly'
+      run: |
+        set -x
+
+        rm -rf main
+        mv html main
+
+        # Update the main doc
+        git add --all main || true
+        git config user.name "pytorchbot"
+        git config user.email "soumith+bot@pytorch.org"
+        git commit -m "auto-generating sphinx docs" || true
+        git push