private URL getSharedFileURL(URL sharedProjectURL, String ref) {
		try {
			// Direct URL construction done so that ghidra protocol extension may be supported
			String urlStr = sharedProjectURL.toExternalForm();
			if (urlStr.endsWith(FileSystem.SEPARATOR)) {
				urlStr = urlStr.substring(0, urlStr.length() - 1);
			}
			urlStr += getPathname();
			return new URL(urlStr);
		}
		catch (MalformedURLException e) {
			// ignore
		}
		return null;
	}
Implements the DomainFile interface for DomainObjects that are not currently
associated with any real DomainFile. This class enforces the sharing of
objects between tools.  After the first tool gets the implementation, all
other gets() just get the same instance.  This class also keeps track of
which tools are using a its domain object.
Ghidra/Framework/Project/src/main/java/ghidra/framework/data/DomainFileProxy.java