xmllint fails to include resources from documents with UNC paths starting with '//'
Lines 2411 and 2412 of uri.c discard the first slash of pathnames starting with two slashes.
However that breaks the external entity loader (for XInclude processing) when an XML document is passed to xmllint as UNC pathname using slashes on Windows, e.g., //host/path/file.xml that contains <xi:include href="resource.xml"/>
.
The source infoset (file.xml) itself is opened but the resource cannot be merged into the result infoset, as the XML base (//host/path/) is crippled by the canonicalization, leaving /host/path/resource.xml, thus triggering a failed to load external entity warning.