If I understand your question correctly, you're asking for what is the default behaviour of Wget.
Wget will only add the extension to the local copy, if the --adjust-extension
option has been passed to it. Quoting the man page for Wget:
--adjust-extension
If a file of type application/xhtml+xml or text/html is downloaded and the URL does not end with the regexp \.[Hh][Tt][Mm][Ll]?, this option will cause the suffix .html to be appended to the
local filename. This is useful, for instance, when you're mirroring a remote site that uses .asp pages, but you want the mirrored pages to be viewable on your stock Apache server. Another good
use for this is when you're downloading CGI-generated materials. A URL like http://example.com/article.cgi?25 will be saved as article.cgi?25.html.
However, what you seem to be asking for, that Wget saves example.org/foo
as /foo/index.html
is actually the default option. If you're seeing some other output, you should post the complete output of Wget with the --debug
switch.