build pkgdown previews on every PR (#307)

.github/workflows/pkgdown.yaml

@@ -3,8 +3,6 @@
 on:
   push:
     branches: main
-  pull_request:
-    branches: main
   release:
     types: [published]
   workflow_dispatch:
@@ -45,6 +43,10 @@ jobs:
         if: github.event_name != 'pull_request'
         uses: JamesIves/github-pages-deploy-action@v4
         with:
-          clean: false
           branch: gh-pages
           folder: docs
+          clean: true
+          force: false
+          clean-exclude: |
+            pr-preview/
+            dev/

.github/workflows/pr-preview-pkgdown.yml

@@ -0,0 +1,44 @@
+# Workflow derived from https://github.com/r-lib/actions/tree/v2/examples
+# Need help debugging build failures? Start at https://github.com/r-lib/actions#where-to-find-help
+on:
+  pull_request:
+    types:
+      - opened
+      - reopened
+      - synchronize
+      - closed
+
+name: pr-preview-pkgdown.yml
+
+concurrency: preview-${{ github.ref }}
+
+jobs:
+  pkgdown:
+    runs-on: ubuntu-latest
+
+    steps:
+      - uses: actions/checkout@v4
+
+      - uses: r-lib/actions/setup-pandoc@v2
+
+      - uses: r-lib/actions/setup-r@v2
+        with:
+          use-public-rspm: true
+
+      - uses: r-lib/actions/setup-r-dependencies@v2
+        with:
+          extra-packages: any::pkgdown, local::.
+          needs: website
+
+      - name: Build site
+        run: pkgdown::build_site_github_pages(new_process = FALSE, install = FALSE)
+        shell: Rscript {0}
+
+      - name: Deploy PR preview to GitHub pages
+        if: ${{ github.event_name == 'pull_request' }}
+        uses: rossjrw/pr-preview-action@v1
+        with:
+          source-dir: docs
+          preview-branch: gh-pages
+          umbrella-dir: pr-preview
+          action: auto