[RFA] New substitute-path commands

[Eli Zaretskii]

> Date: Thu, 13 Jul 2006 14:27:46 -0700
> From: Joel Brobecker <brobecker@adacore.com>
> 
> The interface is as follow:
> 
>         (gdb) set substitute-path FROM TO
>         (gdb) unset substitute-path [FROM]
>         (gdb) show substitute-path
> 
> The "set" command will add a substitution rule.

If this _adds_ a rule, then "set SOMETHING" is not a good UI, IMO.
How about just "substitute-path", similar to "dir", which also _adds_
a directory?

> Actually, as I'm writing this, I now favor first-entered/first-used.
> One can delete a rule if he wants to override it.

Agreed.  Let's just make the logic clear in the manual.