When juggling the setup of several git repositories it's easy to forget to configure the adequate e-mail address you want associated with your commits. Personally, I am guilty of regularly adding the address of my personal projects onto work commits, and vice-versa. Be aware that you are rewriting git history by using this.

change_git_authorship.sh

#!/bin/sh

git filter-branch --env-filter '

an="$GIT_AUTHOR_NAME"
am="$GIT_AUTHOR_EMAIL"
cn="$GIT_COMMITTER_NAME"
cm="$GIT_COMMITTER_EMAIL"

if [ "$GIT_COMMITTER_EMAIL" = "the_dude@ibowl.com" ]
then
    cn="The Dude"
    cm="el_duderino@ibowl.com"
fi
if [ "$GIT_AUTHOR_EMAIL" = "the_dude@ibowl.com" ]
then
    an="The Dude"
    am="el_duderino@ibowl.com"
fi

export GIT_AUTHOR_NAME="$an"
export GIT_AUTHOR_EMAIL="$am"
export GIT_COMMITTER_NAME="$cn"
export GIT_COMMITTER_EMAIL="$cm"
'

This is a personal copy of the solution I found here.