[CI] Run whitespace check on GitHub Actions and annotate source code

.github/workflows/Whitespace.yml

@@ -0,0 +1,23 @@
+name: Whitespace
+
+permissions: {}
+
+on:
+  push:
+    branches:
+      - master
+  pull_request:
+
+jobs:
+  whitespace:
+    name: Check whitespace
+    runs-on: ubuntu-latest
+    timeout-minutes: 2
+    steps:
+      - name: Checkout the JuliaLang/julia repository
+        uses: actions/checkout@692973e3d937129bcbf40652eb9f2f61becf3332 # v4.1.7
+        with:
+          persist-credentials: false
+      - name: Check whitespace
+        run: |
+          contrib/check-whitespace.jl

contrib/check-whitespace.jl

@@ -18,6 +18,8 @@ const patterns = split("""
     *Makefile
 """)
 
+const is_gha = something(tryparse(Bool, get(ENV, "GITHUB_ACTIONS", "false")), false)
+
 # Note: `git ls-files` gives `/` as a path separator on Windows,
 #   so we just use `/` for all platforms.
 allow_tabs(path) =
@@ -63,8 +65,14 @@ function check_whitespace()
         for (path, lineno, msg) in sort!(collect(errors))
             if lineno == 0
                 println(stderr, "$path -- $msg")
+                if is_gha
+                    println(stdout, "::warning title=Whitespace check,file=", path, "::", msg)
+                end
             else
                 println(stderr, "$path:$lineno -- $msg")
+                if is_gha
+                    println(stdout, "::warning title=Whitespace check,file=", path, ",line=", lineno, "::", msg)
+                end
             end
         end
         exit(1)