Bug 11317 Won't export some files to .jar.
Create a new java project called "Foo". In the file system, create a folder named "Foo scripts", and in this folder create a file named "foo.txt". Drag this folder into the eclipse packages view and add it to the "Foo" project. Now try to export the project "Foo" to a .jar file. Only the manifest file shows up, even if the file "foo.txt" is checked!
org.eclipse.jdt.ui/ui/org/eclipse/jdt/internal/ui/jarpackager/JarFileExportOperation.java
if (folderPath.isValidPath(folderPath.toString()) && folderPath.segmentCount() >= 2)
			return JavaPlugin.getWorkspace().getRoot().getFolder(folderPath);
		else
			return null;
	}
	/**
	 * Returns the status of this operation.
	 * If there were any errors, the result is a status object containing
	 * individual status objects for each error.
	 * If there were no errors, the result is a status object with error code <code>OK</code>.
	 *
	 * @return the status of this operation
	 */
	public IStatus getStatus() {
		if (fProblems.getSeverity() == IStatus.ERROR) {
			String message= null;
			if (fDescriptionFiles != null && fDescriptionFiles.length > 1)
				message= JarPackagerMessages.getString("JarFileExportOperation.creationOfSomeJARsFailed"); 
			else
				message= JarPackagerMessages.getString("JarFileExportOperation.jarCreationFailed"); 
			
			return new MultiStatus(JavaPlugin.getPluginId(), 0, fProblems.getChildren(), message, null);
		}
			return fProblems;
	}
	/**
	 * Answer a boolean indicating whether the passed child is a descendant
	 * of one or more members of the passed resources collection
	 *
	 * @param	resources	a List contain potential parents