+ // lualatex can still produce a DVI with --output-format=dvi. However,
+ // we do not use that internally (we use the "dvilualatex" command) so
+ // it would only happen from a custom converter. Thus, it is better to
+ // guess that lualatex produces a PDF than to guess a DVI.
+ // FIXME we should base the extension on the output format, which we should
+ // get in a robust way, e.g. from the converter.
+ if (prefixIs(cmd, "pdf") || prefixIs(cmd, "lualatex") || prefixIs(cmd, "xelatex")) {