Only warn about duplicate menu entries if priorities are equal

When we try to add menu items with the same path and their priorities
differ, we should not complain (the higher-priority one was already
added in that case, so we do not have to replace any existing item).

Signed-off-by: Johannes Schindelin <johannes.schindelin@gmx.de>

Author: dscho

src/main/java/org/scijava/menu/ShadowMenu.java

@@ -530,8 +530,15 @@ private ShadowMenu addChild(final ModuleInfo info, final int depth) {
 		if (!leaf) child.addChild(info, depth + 1);
 		else if (existingChild != null) {
 			if (log != null) {
-				log.warn("ShadowMenu: menu item already exists:\n\texisting: " +
-					existingChild.getModuleInfo() + "\n\t ignored: " + info);
+				if (info.getPriority() == existingChild.getModuleInfo().getPriority()) {
+					log.warn("ShadowMenu: menu item already exists:\n\texisting: " +
+						existingChild.getModuleInfo() + "\n\t ignored: " + info);
+				}
+				else {
+					log.debug("ShadowMenu: higher-priority menu item already exists:\n" +
+						"\texisting: " + existingChild.getModuleInfo() + "\n\t ignored: " +
+						info);
+				}
 			}
 		}
 		return child;