If you want to configure your git mail on a per-repository basis, create this git alias:

mailconfig = !sh -c 'git config user.email $(whiptail --title "git email configuration" --menu "Choose an email address" 20 78 10 --noitem   "mail@server1.com" 1   "mail@server2.com" 2   3>&2 2>&1 1>&3)'

Of course, you can add as many addresses as you want (“mail” number)

Usage:

# In a git repository
git mailconfig