By default, makeinfo splits HTML output into one output file
per Texinfo source node.
When splitting, the HTML output files are written into a subdirectory.
The subdirectory is named according to the name from
@setfilename with any extension removed; for example, HTML
output for @setfilename emacs.info would be written into a
subdirectory named emacs. If that directory cannot be created
for any reason, then .html is appended to the directory name, as
in emacs.html (this is necessary because sometimes the info file
is named without an extension, e.g., texinfo). If the
name.html directory can't be created either,
makeinfo gives up. In any case, the top-level output file within
the directory is always named index.html.
Monolithic output (--no-split) is named according to
@setfilename or --outfile.
@xref commands to other documents are generated assuming the
other document is available in split HTML form, and installed in the
same HTML documentation tree, at ../<info-document>/.
Cross-document node references are not supported in monolithic HTML.