Fixes to the GitHub Actions (#28)

Author: favonia

.github/workflows/ocaml.yml

@@ -1,22 +1,21 @@
-name: Upload the website
+name: Build, test, and doc update
 on:
   push:
     branches:
       - master
   pull_request:
-    branches:
-      - doc*
 jobs:
   run:
+    if: ${{ github.ref == 'refs/heads/master' || (github.event_name == 'pull_request' && startsWith (github.head_ref, 'doc')) }}
     runs-on: ubuntu-latest
     steps:
     - uses: actions/checkout@v2
     - uses: avsm/setup-ocaml@v1
       with:
         ocaml-version: '4.10.0'
     - run: opam pin . --with-test --with-doc -y
-    - run: echo '::set-env name=BUILD_ROOT::'`opam config var yuujinchou:build`
+    - run: echo '::set-env name=opam-build-root::'`opam config var yuujinchou:build`
     - uses: peaceiris/actions-gh-pages@v3
       with:
         github_token: ${{ secrets.GITHUB_TOKEN }}
-        publish_dir: ${{ format('{0}/_build/default/_doc/_html/', env.BUILD_ROOT) }}
+        publish_dir: ${{ format('{0}/_build/default/_doc/_html/', env.opam-build-root) }}