Try to avoid merging with previously generated manifests

git-svn-id: https://svn.apache.org/repos/asf/felix/trunk@1185296 13f79535-47bb-0310-9956-ffa450edef68
diff --git a/bundleplugin/src/main/java/org/apache/felix/bundleplugin/BundlePlugin.java b/bundleplugin/src/main/java/org/apache/felix/bundleplugin/BundlePlugin.java
index 69d0fab..67f9163 100644
--- a/bundleplugin/src/main/java/org/apache/felix/bundleplugin/BundlePlugin.java
+++ b/bundleplugin/src/main/java/org/apache/felix/bundleplugin/BundlePlugin.java
@@ -621,9 +621,10 @@
 
             Manifest mavenManifest = new Manifest();
 
-            // First grab the external manifest file (if specified)
+            // First grab the external manifest file (if specified and different to target location)
             File externalManifestFile = archiveConfig.getManifestFile();
-            if ( null != externalManifestFile && externalManifestFile.exists() )
+            if ( null != externalManifestFile && externalManifestFile.exists()
+                && !externalManifestFile.equals( new File( manifestLocation, "MANIFEST.MF" ) ) )
             {
                 InputStream mis = new FileInputStream( externalManifestFile );
                 mavenManifest.read( mis );