fixup! [docs] Build w/GH Actions and deploy w/GH Pages

.github/main.workflow

@@ -14,14 +14,8 @@ workflow "Build & Publish Documentation Website" {
   resolves = ["website-build-and-publish"]
 }
 
-action "master branch only" {
-  uses = "actions/bin/filter@master"
-  args = "branch master"
-}
-
 action "website-build-and-publish" {
   uses = "./tools/docker/documentation"
   runs = ["/bin/bash", "tools/ci/website_build.sh"]
   secrets = ["DEPLOY_TOKEN"]
-  needs = ["master branch only"]
 }

tools/ci/website_build.sh

@@ -4,17 +4,46 @@ set -x
 
 neutral_status=78
 source_revision=$(git rev-parse HEAD)
+# The token available in the `GITHUB_TOKEN` variable may be used to push to the
+# repository, but GitHub Pages will not rebuild the website in response to such
+# events. Use an access token generated for the project's machine user,
+# wpt-pr-bot.
+#
+# https://help.github.com/en/articles/generic-jekyll-build-failures
+remote_url=https://${DEPLOY_TOKEN}@github.com/web-platform-tests/wpt-actions-test.git
+
+function json_property {
+  cat ${1} | \
+    python -c "import json, sys; print json.load(sys.stdin).get(\"${2}\", \"\")"
+}
+
+function is_pull_request {
+  test -n $(json_property ${GITHUB_EVENT_PATH} pull_request)
+}
+
+function targets_master {
+  test $(json_property ${GITHUB_EVENT_PATH} ref) == '/refs/heads/master'
+}
 
 function modifies_relevant_files {
-  base_revision=$(
-    cat ${GITHUB_EVENT_PATH} | \
-      python -c 'import json, sys; print json.load(sys.stdin)["before"]'
-  )
+  base_revision=$(json_property ${GITHUB_EVENT_PATH} before)
 
   git diff --name-only ${base_revision} | \
     grep -E --silent '^(docs|tools)/'
 }
 
+if is_pull_request ; then
+  echo Submission comes from a pull request. Exiting without building.
+
+  exit ${neutral_status}
+fi
+
+if ! targets_master ; then
+  echo Submission does not target the 'master' branch. Exiting without building.
+
+  exit ${neutral_status}
+fi
+
 if ! modifies_relevant_files ; then
   echo No files related to the website have been modified. Exiting without
   echo building.
@@ -35,6 +64,12 @@ cd _build/html
 
 git init
 
+git fetch --depth 1 ${remote_url}
+
+git checkout FETCH_HEAD
+
+git rm -r .
+
 # Configure DNS
 echo web-platform-tests.org > CNAME
 
@@ -44,18 +79,8 @@ touch .nojekyll
 
 git add .
 
-cat <<HERE |
-Build documentation
+git commit --message "Build documentation
 
-These files were generated from commit ${source_revision}
-HERE
-git commit --file -
+These files were generated from commit ${source_revision}"
 
-# The token available in the `GITHUB_TOKEN` variable may be used to push to the
-# repository, but GitHub Pages will not rebuild the website in response to such
-# events. Use an access token generated for the project's machine user,
-# wpt-pr-bot.
-#
-# https://help.github.com/en/articles/generic-jekyll-build-failures
-git push --force \
-  https://${DEPLOY_TOKEN}@github.com/web-platform-tests/wpt-actions-test.git master:gh-pages
+git push --force ${remote_url} HEAD:gh-pages