I think I have seen convincing arguments _against_ <pre tab-width=4>.
The value does not bear the cost of deployment.
Actually... now that I think about it, the problem of implementing:
<a href="foo.c">foo.c</a>
has nothing to do with HTML at all: that's a text/plain body. You'd
have to convince the browser to display tabs in plain text documents
at every 4 spaces. So you'd have to put the info in the link, or
in a preference setting in the browser or (if there were a server
involved) on the Content-Type header, ala:
0200 ca va bien
Content-Type: text/plain; tabs=4
main()
{
...
Dan