Change the default comments in GIT's COMMIT_EDITMSG after typing "git commit"

Sometimes when I'm at work, I want to commit and push changes to my own projects on GitHub. So I do a lot of git config user.email to make sure that I don't *commit* with my email at the company and that I in fact use my own personal email. Now I have export GIT_EDITOR=vim in my ~/.zshrc file, so that every time I type git commit, vim opens up and I see a file like this:

my actual commit message
# Please enter the commit message for your changes. Lines starting
# with '#' will be ignored, and an empty message aborts the commit.
#
# On branch master
# Your branch is up to date with 'origin/master'.
#
# Changes to be committed:
#         modified:    vim/.vimrc
#

Is there a way that I can modify these comments? So that it shows something like this:

my actual commit message
# Email: me@my.site
#
# On branch master
# Your branch is up to date with 'origin/master'.
#
# Changes to be committed:
#         modified:    vim/.vimrc
#