Add log warning in AgentJarIndex if an entryKey has multiple prefixIds. (#8434)

* Add log warning if entryKey has multiple prefixIds.

* Only warn if prefixId changes.

* Improve log warning to describe the situation instead of the state.

* Update log warning message.

Co-authored-by: Stuart McCulloch <stuart.mcculloch@datadoghq.com>

---------

Co-authored-by: Stuart McCulloch <stuart.mcculloch@datadoghq.com>

Author: sarahchen6

dd-java-agent/agent-bootstrap/src/main/java/datadog/trace/bootstrap/AgentJarIndex.java

@@ -142,6 +142,12 @@ public FileVisitResult visitFile(Path file, BasicFileAttributes attrs) {
       if (null != prefixRoot) {
         String entryKey = computeEntryKey(prefixRoot.relativize(file));
         if (null != entryKey) {
+          int existingPrefixId = prefixTrie.apply(entryKey);
+          if (-1 != existingPrefixId && prefixId != existingPrefixId) {
+            log.warn(
+                "Detected duplicate content under '{}'. Ensure your content is under a distinct directory.",
+                entryKey);
+          }
           prefixTrie.put(entryKey, prefixId);
           if (entryKey.endsWith("*")) {
             // optimization: wildcard will match everything under here so can skip