How to not change the working directory when opening a file

[Francis Moreau]

Hello list,

I'd like Emacs to not changing the working directory when opening
a file.

For example when doing:

$ pwd
/home/fmoreau/tmp
$ emacs /tmp/foo.txt

I'd like the current working directory to be "/home/fmoreau/tmp"
when editing "/tmp/foo.txt" in emacs.

This is useful when composing an email. I sometime need to
include the output of a shell command but this shell command
must be executed in the directory where emacs was launched.

Does anybody can give me a hint to do that ?

Thanks
--
Francis