Multiple Git accounts with different SSH keys

It's quite simple to setup multiple Git (in this case GitHub) accounts on the same machine, each using different SSH keys. The scenario that I use this for is to have both a personal account and a work account.

Host github-personal
	HostName github.com
    IdentityFile ~/.ssh/personal_github_key
    
Host github-work
	HostName github.com
    IdentityFile ~/.ssh/work_github_key

You also need to set your remotes to use the above Host.

When you clone you need to change this:

git clone git@github.com:personal-org/repo.git

to this:

git clone git@github-personal:personal-org/repo.git

If you already have a repo you can change the remote addresses.

// see what is currently set
git remote -v

git remote set-url origin git@github-personal:personal-org/repo.git

Different Emails for GitHub

Something else that you may run into is GitHub showing the wrong user in the commit history. This was happening for me because of the email address used in .gitconfig

You may have set this using:

git config --global user.email "some@email.com"

GitHub uses this email to tie a commit to a GitHub account. This caught me by surprise as I thought it would match based on the ssh key used.

In order to fix this we can add some conditionals to our .gitconfig

[user]
	email = personal@email.com
    name = Personal Name
    signingkey = <personal signing key>
    
[includeIf "gitdir:company-projects/"]
	path .gitconfig-work

This sets up a default configuration and tells git to load .gitconfig-work if your current path includes "company-projects/"

email = business@email.com
name = Work Name
signingkey = <work signing key>

New commits should now be shown as the correct user.