Using different emails and GPG keys for work and personal stuff on GitHub

.gitconfig

[core]
  # ...

[init]
  defaultBranch = main

[commit]
  gpgsign = true

# you want that to have a default for locations outside of your regular dev folders
[include]
  path = ~/.gitconfig.personal

# IMPORTANT: Yes, the trailing slash is required!
[includeIf "gitdir:~/Development/Personal/"]
  path = ~/.gitconfig.personal

[includeIf "gitdir:~/Development/Work/"]
  path = ~/.gitconfig.work

.gitconfig.personal

[user]
  name = <YOUR NAME>
  email = <YOUR MAIN/PERSONAL EMAIL>
  signingkey = <YOUR GPG KEY FOR PERSONAL EMAIL>

.gitconfig.work

[user]
  name = <YOUR NAME>
  email = <YOUR WORK EMAIL>
  signingkey = <YOUR GPG KEY FOR WORK EMAIL>

# this switches the host for SSH and therefore also selects desired SSH key
[url "git@github.com-work"]
  insteadOf = git@github.com

_ssh_config

# ~/.ssh/config
Host github.com
  Hostname github.com
  User <YOUR GITHUB USERNAME>
  IdentityFile <PATH TO YOUR MAIN KEY>
  IdentitiesOnly yes

Host github.com-work
  Hostname github.com
  User <YOUR GITHUB USERNAME>
  IdentityFile <PATH TO YOUR WORK KEY>
  IdentitiesOnly yes

Host *
  PreferredAuthentications publickey
  Compression yes
  ServerAliveInterval 30
  ServerAliveCountMax 9999
  VisualHostKey yes
  AddKeysToAgent yes

NOTES.md

If you want to use different SSH keys: https://xiaolishen.medium.com/use-multiple-ssh-keys-for-different-github-accounts-on-the-same-computer-7d7103ca8693

Slight difference to the guide:
With the .gitconfig.work you do not need to change the URL during cloning.
The config [url …] will do that for you already automatically.
Once in a work repo you can check it with git remote -v and you see the rewritten URLs.