Expand checking workflows to more platforms

Author: andrjohns

.github/workflows/R-CMD-check.yaml

@@ -18,11 +18,15 @@ jobs:
       fail-fast: false
       matrix:
         config:
+          - {os: macos-latest,   r: 'devel'}
           - {os: macos-latest,   r: 'release'}
+          - {os: macos-latest,   r: 'oldrel'}
+          - {os: windows-latest, r: 'devel'}
           - {os: windows-latest, r: 'release'}
-          - {os: ubuntu-latest,   r: 'devel', http-user-agent: 'release'}
+          - {os: windows-latest, r: 'oldrel'}
+          - {os: ubuntu-latest,   r: 'devel'}
           - {os: ubuntu-latest,   r: 'release'}
-          - {os: ubuntu-latest,   r: 'oldrel-1'}
+          - {os: ubuntu-latest,   r: 'oldrel'}
 
     env:
       GITHUB_PAT: ${{ secrets.GITHUB_TOKEN }}
@@ -36,7 +40,6 @@ jobs:
       - uses: r-lib/actions/setup-r@v2
         with:
           r-version: ${{ matrix.config.r }}
-          http-user-agent: ${{ matrix.config.http-user-agent }}
           use-public-rspm: true
 
       - uses: r-lib/actions/setup-r-dependencies@v2