Bug 37197 Basepath for relative pathes in JAR-exporter
The basepath for the JAR-exporter is the eclipse-install-directory. I prefer it to be the root of the project (the description is saved in), so that relative pathes end inside the project. Now: <jardesc> <jar path="workspace/projectdir/jar.jar"/> Desired: <jardesc> <jar path="jar.jar"/> Reason: To make the jardesc-files portable for shared projects
org.eclipse.jdt.ui/ui/org/eclipse/jdt/internal/ui/jarpackager/JarPackageWizardPage.java
setErrorMessage(null);
			if (getMessage() != null)
				setMessage(null);
			return false;
		}
		if (fJarPackage.getJarLocation().toString().endsWith("/")) { 
			setErrorMessage(JarPackagerMessages.getString("JarPackageWizardPage.error.exportDestinationMustNotBeDirectory")); 
			fDestinationNamesCombo.setFocus();
			return false;
		}
		if (getWorkspaceLocation() != null && getWorkspaceLocation().isPrefixOf(fJarPackage.getJarLocation())) {
			int segments= getWorkspaceLocation().matchingFirstSegments(fJarPackage.getJarLocation());
			IPath path= fJarPackage.getJarLocation().removeFirstSegments(segments);
			IResource resource= ResourcesPlugin.getWorkspace().getRoot().findMember(path);
			if (resource != null && resource.getType() == IResource.FILE) {
				
				if (JarPackagerUtil.contains(JarPackagerUtil.asResources(fJarPackage.getElements()), (IFile)resource)) {
					setErrorMessage(JarPackagerMessages.getString("JarPackageWizardPage.error.cantExportJARIntoItself")); 
					return false;
				}
			}
		}
		
		String currentMessage= getMessage();
		if (!(new File(fDestinationNamesCombo.getText()).isAbsolute())) {
			if (currentMessage == null)
				setMessage(JarPackagerMessages.getString("JarPackageWizardPage.info.relativeExportDestination"), WizardPage.INFORMATION); 
		} else {
			if (currentMessage != null)
				setMessage(null);