Having different Git repositories, I used to configure user.email and user.name on a per repository basis to avoid commiting with the wrong identity. It was always a bit cubersome to set up when having a new repository.
I recently stumbled upon the Git includeIf config (available since Git 2.13) which allows loading an overriding configuration file depending on the repository location.
In practice, I now have a global personal ~/.gitconfig with:
[user]
name = My name
email = user.name@personal.example
[includeIf "gitdir:~/work/"]
path = ~/.gitconfig.work
and in ~/.gitconfig.work:
[user]
name = My name
email = user.name@work.example
That way, all repositories located in ~/work automatically inherits that configuration and I do not have to setup per repository settings.
Some resources: