This article was originally published in our UncaughtException blog. Read this article in there by following this link.

Cover photo by Brina Blum on Unsplash.

I previously wrote about setting up multiple GitLab accounts, which works by relying mostly on SSH config files and using custom hosts as remotes for git repositories. You can read it by following this link: Setting up multiple GitLab accounts

The previous setup works, but I find it inconvenient having to use custom hosts when cloning repositories or for git remotes all the time, like:

$ git clone git@gitlab.com-work:work/repository.git

I recently (almost) had to deal with the same scenario, on GitHub this time (hence the title), so I decided to check if I can achieve a better setup. Turns out that there’s a better way to do it — one that does not rely on custom hosts or modifying any SSH config file.

In this article, we are going to assume that we have two GitHub accounts, personal@email.com and work@email.com. When working on work-related projects we want to commit and push our changes using our work account, while using our personal account for everything else.

We’re also going to assume that we’ve already defined global configs telling git to use our personal account. See this guide on how to do that.

Generate SSH keys for each user

GitHub does not allow us to use the same SSH key in multiple accounts, so we’ll have to create separate keys for each account. We can create SSH keys and add them to our SSH agent by following this guide from the GitHub Documentation.

Once we’re done, we will have two sets of SSH keys, e.g.:

• ~/.ssh/id_rsa and ~/.ssh/id_rsa.pub (let’s use this for our personal account)
• ~/.ssh/work_key and ~/.ssh/work_key.pub

Now add the SSH keys to their corresponding GitHub accounts. This guide shows us how to do that.

Committing as the correct user

We then modify our ~/.gitconfig file to use our work account when we are inside a work-related repository. We are going to use “Conditional Includes” for that, which dynamically adds/removes configuration based on certain conditions. Let’s add the following snippet to our ~/.gitconfig file:

[includeIf "gitdir:/path/to/work/repository/"]
    [user]
        email = "work@email.com"

This makes git override our global configs and use work@email.com when committing changes inside the work repository. When in any other repository, our personal account will be used.

Do this for all work repositories

The way I personally structure my repositories on my file system is I place all work-related repositories inside the ~/work directory. This makes it easier to enable the configs above for all work-related repositories by just using the work directory in the includeIf directive:

[includeIf "gitdir:~/work/"]

Pushing as the correct user

When we push our commits now, they will be pushed to our personal GitHub account, even though we’ve already committed them using our work email. That’s because under the hood, git uses SSH, and SSH uses the id_rsa key by default. So when GitHub receives the push, it will try to determine which user pushed the commits based on the SSH key used, which will turn out to be our personal account.

We can resolve this by using the work_key SSH key when pushing to our work repositories. In SSH, this can be done through the -i flag, like so:

$ ssh -i ~/.ssh/work_key ...

We can configure git to use a custom SSH command like above by setting core.sshCommand. And since we only want to set it when we’re inside any work repository, we also conditionally include it inside the includeIf directive:

[includeIf "gitdir:/path/to/work/repository/"]
    [user]
        email = "work@email.com"
    [core]
        sshCommand = "ssh -i ~/.ssh/work_key"

These configs now make git commit using our work email, as well as make GitHub associate commits with our work account when we push them 🎉.

Summary

We’ve managed to configure git to use different configs when committing and associating these commits to different GitHub accounts when pushing, based on what repository we are performing those changes — and we used conditional includes in git’s config file to achieve that.

I like this way better than the previous setup since it’s more convenient to use (no more custom hosts) and all the config changes only affect git (no more changing of SSH config files).

If you deal with these multiple GitHub accounts in a different way, please feel free to share with us how you do it as well!