Not everyone has the luxury of using their personal Github account for all their projects. It's quite common to have a company provided account as well as a few personal accounts. Without the proper local setup this can cause all kinds of issues: having to login every push, authentication errors, commits associated with the "wrong" account, etc. For those of us unfamiliar with git and/or ssh, wrangling multiple identities can be a daunting task but it's actually quite simple.
If you don't already use ssh for cloning and authentication then you will need to switch to that. While it requires some setup, no longer having to login to perform git actions is quite convenient.
Let's assume you have a work account and a personal account. If you don't already have ssh keys for these accounts follow this handy guide provided by Github. Once you've created both keys, add them to your respective Github accounts.
Your ~/.ssh directory should now look something like this:
.ssh/
|-- id_rsa_work
|-- id_rsa_work.pub
|-- id_rsa_personal
|-- id_rsa_personal.pub
There should be a public and private key for both of your accounts. If not, you may have overwritten the first set with the second.
If your ~/.ssh directory doesn't already contain a config file you'll need to create one (~/.ssh/config). It should look something like this:
Host github.com-work
HostName github.com
User git
AddKeysToAgent yes
IdentityFile ~/.ssh/id_rsa_work
Host github.com-personal
HostName github.com
User git
AddKeysToAgent yes
IdentityFile ~/.ssh/id_rsa_personal
At first glance, this configuration may seem confusing but cloning a couple repos should clear things up.
Suppose you have a clone URL for a work repo like this:
git@github.com:my-company/work-repo.git
You'd need to change it to this:
git@github.com-work:my-company/work-repo.git
Notice how the host has changed from github.com to github.com-work. It's the same host that was specified in the config file. This tells ssh that the id_rsa_work key should be used for this repo and to map the custom github.com-work host to the actual host github.com. Now, to ensure that you're committing and pushing with the right identity, cd into the work-repo directory and setup a local git config.
git config user.name "my-work-username"
git config user.email "my-work-email"
As we are not using the --global flag, these commands only set the identity for the work-repo repo. You will not have to set this configuration again unless you delete the directory and reclone.
You can perform the process again for your personal repo swapping out the github.com-work custom host with github.com-personal, your work username for your personal username, and your work email for your personal email.
This process can be repeated for any number of identities, adding a "block" in the ssh config file for each.