WIP: add whitespace check

Author: simeonschaub

.github/workflows/whitespace.yml

@@ -0,0 +1,31 @@
+name: Whitespace Check
+# Run only on pull requests
+on:
+  pull_request:
+jobs:
+  check-whitespace:
+    name: Check Whitespace
+    runs-on: ubuntu-latest
+    steps:
+      run: | # adapted from https://github.com/JuliaLang/julia/blob/f5ce7c4cb9b3e2140819b6b089530ee69aea3d2f/contrib/check-whitespace.sh
+        set -f # disable glob expansion in this script
+        file_patterns='
+        *.jl
+        *.md
+        *.toml
+        *.yml
+        '
+
+        # TODO: Look also for trailing empty lines, and missing '\n' after the last line
+        if git --no-pager grep --color -n --full-name -e ' $' -- $file_patterns; then
+            echo "Error: trailing whitespace found in source file(s)"
+            echo ""
+            echo "This can often be fixed with:"
+            echo "    git rebase --whitespace=fix HEAD~1"
+            echo "or"
+            echo "    git rebase --whitespace=fix master"
+            echo "and then a forced push of the correct branch"
+            exit 1
+        fi
+
+        echo "Whitespace check found no issues"