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
path= getWorkspaceLocation().append(path);
		if (path.segmentCount() > 0 && ensureTargetFileIsValid(path.toFile()) && path.getFileExtension() == null) 
			
			path= path.addFileExtension(JarPackagerUtil.JAR_EXTENSION);
		fJarPackage.setJarLocation(path);
		
		fJarPackage.setCompress(fCompressCheckbox.getSelection());
		fJarPackage.setOverwrite(fOverwriteCheckbox.getSelection());
	}
	/**
	 * Returns a boolean indicating whether the passed File handle is
	 * is valid and available for use.
	 *
	 * @return boolean
	 */
	protected boolean ensureTargetFileIsValid(File targetFile) {
		if (targetFile.exists() && targetFile.isDirectory() && fDestinationNamesCombo.getText().length() > 0) {
			setErrorMessage(JarPackagerMessages.getString("JarPackageWizardPage.error.exportDestinationMustNotBeDirectory")); 
			fDestinationNamesCombo.setFocus();
			return false;
		}
		if (targetFile.exists()) {
			if (!targetFile.canWrite()) {
				setErrorMessage(JarPackagerMessages.getString("JarPackageWizardPage.error.jarFileExistsAndNotWritable")); 
				fDestinationNamesCombo.setFocus();
				return false;
			}
		}
		return true;