Logging fix (#699)

planetiler-core/src/main/java/com/onthegomap/planetiler/util/LogUtil.java

@@ -24,7 +24,8 @@ public static void clearStage() {
 
   /** Returns the current {@code [stage]} value prepended to log for this thread. */
   public static String getStage() {
-    return MDC.get(STAGE_KEY);
+    // strip out the "[stage] " wrapper
+    return MDC.get(STAGE_KEY) instanceof String s ? s.substring(1, s.length() - 2) : null;
   }
 
   /** Prepends {@code [parent:child]} to all subsequent logs from this thread. */

planetiler-core/src/test/java/com/onthegomap/planetiler/util/LogUtilTest.java

@@ -0,0 +1,19 @@
+package com.onthegomap.planetiler.util;
+
+import static org.junit.jupiter.api.Assertions.assertEquals;
+import static org.junit.jupiter.api.Assertions.assertNull;
+
+import org.junit.jupiter.api.Test;
+
+class LogUtilTest {
+  @Test
+  void testStageHandling() {
+    assertNull(LogUtil.getStage());
+    LogUtil.setStage("test");
+    assertEquals("test", LogUtil.getStage());
+    LogUtil.setStage(LogUtil.getStage(), "child");
+    assertEquals("test:child", LogUtil.getStage());
+    LogUtil.clearStage();
+    assertNull(LogUtil.getStage());
+  }
+}