PR commit header validation.

 - simple script to check if all commits have proper email addresses
 - looks for empty or single word subject messages
 - warns about missing blank line after subject
 - logs errors/warnings to the github actions summary page

.github/scripts/CommitHeaderChecker.java

@@ -0,0 +1,114 @@
+/*
+ * Licensed to the Apache Software Foundation (ASF) under one
+ * or more contributor license agreements.  See the NOTICE file
+ * distributed with this work for additional information
+ * regarding copyright ownership.  The ASF licenses this file
+ * to you under the Apache License, Version 2.0 (the
+ * "License"); you may not use this file except in compliance
+ * with the License.  You may obtain a copy of the License at
+ *
+ *   http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing,
+ * software distributed under the License is distributed on an
+ * "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
+ * KIND, either express or implied.  See the License for the
+ * specific language governing permissions and limitations
+ * under the License.
+ */
+
+import java.io.IOException;
+import java.net.URI;
+import java.net.http.HttpClient;
+import java.net.http.HttpClient.Redirect;
+import java.net.http.HttpRequest;
+import java.net.http.HttpResponse.BodyHandlers;
+import java.time.Duration;
+import static java.util.stream.Gatherers.fold;
+import static java.util.stream.Gatherers.scan;
+import static java.util.stream.Gatherers.windowSliding;
+
+record Commit(int index, String from, String date, String subject, String blank) {}
+record Result(int total, boolean green) {}
+
+// java CommitHeaderChecker.java https://github.com/apache/netbeans/pull/${{ github.event.pull_request.number }}
+void main(String[] args) throws IOException, InterruptedException {
+
+    if (args.length != 1 || !args[0].startsWith("https://github.com/")) {
+        throw new IllegalArgumentException("PR URL expected");
+    }
+
+    HttpRequest request = HttpRequest.newBuilder()
+            .uri(URI.create(args[0]+".patch"))
+            .timeout(Duration.ofSeconds(10))
+            .build();
+
+    println("checking commit(s)...");
+    Result result;
+    try (HttpClient client = HttpClient.newBuilder()
+            .followRedirects(Redirect.NORMAL).build()) {
+
+        result = client.send(request, BodyHandlers.ofLines()).body()
+            .gather(windowSliding(4))
+            .filter(w -> w.size() == 4 && w.get(0).startsWith("From: ") && w.get(1).startsWith("Date: ") && w.get(2).startsWith("Subject: "))
+            .gather(scan(
+                () -> new Commit(0, "", "", "", ""),
+                (c, w) -> new Commit(c.index+1, w.get(0), w.get(1), w.get(2), w.get(3))))
+            .gather(fold(
+                () -> new Result(0, true),
+                (r, c) -> new Result(r.total+1, r.green & checkCommit(c))))
+            .findFirst()
+            .orElseThrow();
+    }
+
+    println(result.total + " commit(s) checked");
+    System.exit(result.green ? 0 : 1);
+}
+
+boolean checkCommit(Commit c) {
+    return checkNameAndEmail(c.from, c.index)
+         & checkSubject(c.subject, c.index)
+         & checkBlankLineAfterSubject(c.blank, c.index);
+}
+
+boolean checkNameAndEmail(String from, int i) {
+    // From: Duke <[email protected]>
+    int start = from.indexOf('<');
+    int end = from.indexOf('>');
+
+    String mail = end > start ? from.substring(start+1, end) : "";
+    String author = start > 6 ? from.substring(6, start).strip() : "";
+
+    boolean green = true;
+    if (mail.isBlank() || !mail.contains("@") || mail.contains("noreply") || mail.contains("localhost")) {
+        println("::error::invalid email in commit " + i + " '" + from + "'");
+        green = false;
+    }
+    // single word author -> probably the nickname/account name/root etc
+    // mime encoded is probably fine, since gh account names can't be encoded
+    if (author.isBlank() || (!author.contains(" ") && !(author.startsWith("=?") && author.endsWith("?=")))) {
+        println("::error::invalid author in commit " + i + " '" + author + "' (full name?)");
+        green = false;
+    }
+    return green;
+}
+
+// https://mirrors.edge.kernel.org/pub/software/scm/git/docs/git-commit.html#_discussion
+boolean checkSubject(String subject, int i) {
+    // Subject: [PATCH] msg
+    subject = subject.substring(subject.indexOf(']')+1).strip();
+    // single word subjects are likely not intended or should be squashed
+    if (!subject.contains(" ")) {
+        println("::error::invalid subject in commit " + i + " '" + subject + "'");
+        return false;
+    }
+    return true;
+}
+
+boolean checkBlankLineAfterSubject(String blank, int i) {
+    if (!blank.isBlank()) {
+        println("::warning::blank line after subject recommended in commit " + i + " (subject over 50 char limit?)");
+//        return false;
+    }
+    return true;
+}

.github/workflows/main.yml

@@ -287,7 +287,7 @@ jobs:
       ANT_OPTS: -Dmetabuild.jsonurl=https://raw.githubusercontent.com/apache/netbeans-jenkins-lib/master/meta/netbeansrelease.json
     strategy:
       matrix:
-        java: [ '17' ]
+        java: [ '23' ]
     steps:
 
       - name: Check PR labels
@@ -310,11 +310,10 @@ jobs:
           persist-credentials: false
           submodules: false
           show-progress: false
-          fetch-depth: 10
 
-      - name: Print last 10 Commits
+      - name: Check Commit Headers
         if: ${{ github.event_name == 'pull_request' && !cancelled() }}
-        run: git log --oneline -n10 --pretty=format:'%h %an [%ae] %s'
+        run: java --enable-preview .github/scripts/CommitHeaderChecker.java https://github.com/apache/netbeans/pull/${{ github.event.pull_request.number }}
 
       - name: Check line endings and verify RAT report
         if: ${{ !cancelled() }}