bug#74208: 31.0.50; minibuffer read-file-name-default mutates global value of default-directory incorrectly

[Stefan Monnier]

> Ping! How should we make progress with this issue?

I think the core of this bug report is that `shell-command` can fail
when `default-directory` is set to a value that doesn't correspond to
a local directory.

At least for things like `(shell-command "date")` this is undesirable.

Maybe `call-process` should try to "look for" a valid directory if
`default-directory` isn't good enough?


        Stefan