These instructions assume you have a personal and work email.
The default email will be personal, and all repos in a folder ~/work will be commited to with your work email.
Change ~/work in the details below to whatever you want (ie. your company's name).
Create ~/.gitconfig with the following contents:
[user]
name = <your name>
email = <personal email>
[includeIf "gitdir:~/work/"]
path = ~/work/.gitconfig_include
Create and move into the work folder:
mkdir work && cd work
Create ~/work/.gitconfig_include with the following contents:
[user]
email = <work email>