Avoid including raw content in AbstractPushCommand.toString()

Motivation:

Some push requests may contain large content exceeding 1MB. Including
such large values in `AbstractPushCommand.toString()` is risky. It could
overwhelm the logging buffer or even cause memory leaks if cached.

Modifications:

- Include only contentLength when generating a string representation of a
  push command.

Result:

`*PushCommand.toString()` no longer includes raw content.

Author: ikhoon

server/src/main/java/com/linecorp/centraldogma/server/command/AbstractPushCommand.java

@@ -122,11 +122,28 @@ public int hashCode() {
 
     @Override
     ToStringHelper toStringHelper() {
+        // Build a summary of changes to avoid overly long toString() result.
+        final StringBuilder changesBuilder = new StringBuilder("[");
+        for (int i = 0; i < changes.size(); i++) {
+            final Change<?> change = changes.get(i);
+            final String content = change.contentAsText();
+            changesBuilder.append("{type: ").append(change.type())
+                          .append(", path: ").append(change.path())
+                          .append(", contentLength: ")
+                          .append(content != null ? content.length() : 0)
+                          .append('}');
+            if (i != changes.size() - 1) {
+                changesBuilder.append(", ");
+            }
+        }
+        changesBuilder.append(']');
+
         return super.toStringHelper()
                     .add("baseRevision", baseRevision)
                     .add("summary", summary)
                     .add("detail", detail)
                     .add("markup", markup)
-                    .add("changes", changes);
+                    .add("numChanges", changes.size())
+                    .add("changes", changesBuilder.toString());
     }
 }

server/src/test/java/com/linecorp/centraldogma/server/command/PushCommandTest.java

@@ -0,0 +1,52 @@
+/*
+ * Copyright 2025 LY Corporation
+ *
+ * LY Corporation 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:
+ *
+ *   https://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.
+ */
+
+package com.linecorp.centraldogma.server.command;
+
+import static org.assertj.core.api.Assertions.assertThat;
+
+import java.util.List;
+
+import org.junit.jupiter.api.Test;
+
+import com.fasterxml.jackson.databind.JsonNode;
+import com.google.common.collect.ImmutableList;
+
+import com.linecorp.centraldogma.common.Author;
+import com.linecorp.centraldogma.common.Change;
+import com.linecorp.centraldogma.common.Markup;
+import com.linecorp.centraldogma.common.Revision;
+
+class PushCommandTest {
+
+    @Test
+    void shouldNotContainRawContentInToString() {
+        final Change<JsonNode> json = Change.ofJsonUpsert("/a.json", "{ \"foo\": \"bar\" }");
+        final Change<String> text = Change.ofTextUpsert("/a.txt", "Hello");
+        final Change<Void> removal = Change.ofRemoval("/b.txt");
+        final List<Change<?>> changes = ImmutableList.of(json, text, removal);
+
+        final Command<CommitResult> pushCommand =
+                Command.push(Author.SYSTEM, "myProject", "myRepo",
+                             Revision.HEAD,
+                             "summary", "detail",
+                             Markup.PLAINTEXT, changes);
+        assertThat(pushCommand.toString()).contains(
+                "changes=[{type: UPSERT_JSON, path: /a.json, contentLength: " + json.contentAsText().length() +
+                "}, {type: UPSERT_TEXT, path: /a.txt, contentLength: " + text.contentAsText().length() +
+                "}, {type: REMOVE, path: /b.txt, contentLength: 0}]");
+    }
+}