Export the entries of transitive dependencies

JDT has a concept of exporting classpath entries that can be used when
referencing a project in the remote-debugger, currently no entries are
exported.

This sets the exported flag for all items that are normally transitive
in maven.

org.eclipse.m2e.jdt/src/org/eclipse/m2e/jdt/internal/DefaultClasspathManagerDelegate.java

@@ -148,6 +148,7 @@ void addClasspathEntries(IClasspathDescriptor classpath, IMavenProjectFacade fac
         entry.setArtifactKey(new ArtifactKey(a.getGroupId(), a.getArtifactId(), a.getBaseVersion(), a.getClassifier()));
         entry.setScope(a.getScope());
         entry.setOptionalDependency(a.isOptional());
+        entry.setExported(isExportedArtifact(a));
       }
     }
 
@@ -161,6 +162,19 @@ void addClasspathEntries(IClasspathDescriptor classpath, IMavenProjectFacade fac
     });
   }
 
+  private boolean isExportedArtifact(Artifact a) {
+    if(Artifact.SCOPE_PROVIDED.equals(a.getScope())) {
+      //provided items are not transitive
+      return false;
+    }
+    if(a.isOptional()) {
+      //optional artifacts are also not transitive
+      return false;
+    }
+    //everything else is considered transitive
+    return true;
+  }
+
   private boolean isOnlyVisibleByTests(Artifact a) {
     return Artifact.SCOPE_TEST.equals(a.getScope()) || Artifact.SCOPE_RUNTIME.equals(a.getScope());
   }