git-switch-user.sh

#!/bin/bash

userName="John Doe"
emails=(
    "john@doe.com"
    "john.doe@freelance.com"
    "john.doe@acme.com"
)

if [[ $1 =~ ^[1-9][0-9]*$ ]]
then
    key=$1
    realKey=$(($key - 1))
    email="${emails[${realKey}]}"

    if [ -z "${email}" ]
    then
        echo "User with key ${key} does not exist"

        exit 1
    fi

    git config --global user.name "${userName}"
    git config --global user.email "${email}"
    echo "Changed user to: $(git config user.name) <$(git config user.email)>"
else
    realFirstKey="$(echo ${!emails[@]} | grep -Eo '^[0-9]+')"
    realLastKey="$(echo ${!emails[@]} | grep -Eo '[0-9]+$')"
    firstKey=$(($realFirstKey + 1))
    lastKey=$(($realLastKey + 1))

    echo "Usage: $0 [${firstKey}-${lastKey}]"

    for realKey in ${!emails[@]}
    do
        key=$(($realKey + 1))
        email="${emails[${realKey}]}"
        echo "  ${key} - ${userName} <${email}>"
    done

    echo "Current user: $(git config user.name) <$(git config user.email)>"
fi