Restrict build info loading to ES jar, not any jar (#24049)

This change makes the build info initialization only try to load a jar
manifest if it is the elasticsearch jar. Anything else (eg a repackaged
ES for use of transport client in an uber jar) will contain "Unknown"
for the build info as it does for tests currently.

fixes #21955

Author: rjernst

core/src/main/java/org/elasticsearch/Build.java

@@ -42,8 +42,10 @@ public class Build {
         final String date;
         final boolean isSnapshot;
 
+        final String esPrefix = "elasticsearch-" + Version.CURRENT;
         final URL url = getElasticsearchCodebase();
-        if (url.toString().endsWith(".jar")) {
+        final String urlStr = url.toString();
+        if (urlStr.startsWith("file:/") && (urlStr.endsWith(esPrefix + ".jar") || urlStr.endsWith(esPrefix + "-SNAPSHOT.jar"))) {
             try (JarInputStream jar = new JarInputStream(url.openStream())) {
                 Manifest manifest = jar.getManifest();
                 shortHash = manifest.getMainAttributes().getValue("Change");
@@ -53,7 +55,7 @@ public class Build {
                 throw new RuntimeException(e);
             }
         } else {
-            // not running from a jar (unit tests, IDE)
+            // not running from the official elasticsearch jar file (unit tests, IDE, uber client jar, shadiness)
             shortHash = "Unknown";
             date = "Unknown";
             isSnapshot = true;