allow me to adjust URL before visiting

[jidanni@xxxxxxxxxxx]

Often my cursor is sitting upon a URL, and I want to visit it, but
would like to modify it a little first before visiting it.

So I end up doing e.g.,
u g C-y C-b C-b...C-b C-k <return> (here I have deleted some
characters at the end of the URL)

I would rather do
      X C-b C-b...C-b C-k <return>
where X is some new key-command.

Actually the g command already give the user the opportunity to adjust
the URL before hitting RET. The problem with g is that it acts the
same whether the cursor is sitting on top of a link or not.

By the way, C-h m doesn't give the full list of emacs-w3m commands.
One needs C-h b to see them.