tracking cd commands in a shell

[Daniel R. Grayson]

> Try this in a shell buffer and afterwards, emacs thinks your buffer is still
> in /tmp.
> 
>     rhenium% id
>     uid=102(dan) gid=100(users) 
> groups=100(users),17(apm),50(software),121(Macaulay),200(family)
>     rhenium% cd /tmp
>     rhenium% mkdir '~dan'
>     rhenium% cd '~dan'
>     rhenium% 
> 
> In GNU Emacs 20.7.1 (i486-pc-linux-gnu, X toolkit)
>  of Tue Jan  2 2001 on rhenium
> configured using `configure  i486-linux-gnu'

A bit more precise: afterwards, when you try to visit a file, called foo,
say, the name of the file,

        /tmp/~dan/foo

is translated into

        ~dan/foo

incorrectly.