How to prepare your git environment to work:

• with different auth ssh and signing gpg keys
• with different git hosts (e.g. GitHub, GitLab) and organization (private account, company account)
• with automatic key selection based on the folder path and ssh host

Steps:

1. Generate new SSH private key(s)

   • Generating a private key with a passphrase is a requirement on Mac ⚠️

     $ ssh-keygen -t ED25519 -C "your@github.email" -f ~/.ssh/id_org1_github
     $ pbcopy ~/.ssh/id_org1_github.pub
     $ open https://github.com/settings/keys
     
     $ ssh-keygen -t ED25519 -C "your@gitlab.email" -f ~/.ssh/id_org3_gitlab
     $ pbcopy ~/.ssh/id_org3_gitlab.pub
     $ open https://gitlab.com/-/profile/keys

   • Make keys "persistent" automatically loaded after Mac reboot
   • Update ~/.ssh/config file:

     Host *
         UseKeychain yes
         AddKeysToAgent yes
         IgnoreUnknown UseKeychain
     
     Host org1-github
         user = git
         HostName = github.com
         identityfile = ~/.ssh/id_org1_github
         identitiesonly yes           
     
     Host org3-gitlab
         HostName = gitlab.com
         user = git
         identityfile = ~/.ssh/id_org3_gitlab
         identitiesonly yes
     

   • For GitHub make sure you authorized your ssh key with your organization via SSO

2. Generate new GPG signing key(s)

   • Execute

     $ gpg --gen-key

   • Note your GPG key ID, It begins after the / character in the sec paragraph after executing:

     $ gpg --list-secret-keys --keyid-format LONG first.last@organisation1.com
     sec   rsa3072/<GPG KEY ID IS HERE> 2022-03-03 [SC]
           5A233D97F169400541080D50D58FC20EB4027CXX
     uid                 [ultimate] first last <first.last@organisation1.com>
     ssb   rsa3072/560358F2315DB6XX 2022-03-03 [E]

3. Set up ~/.gitconfig so that it automatically picks up your git config based on the folder prefix

• We suggest to follow folder paths for all git repositories

  ~/Projects
  ├── github
  │   ├── my-organisation1
  │   │   ├── repo-1
  │   │   └── ...
  │   └── my-organisation2
  │       ├── repo-2
  │       └── ...
  ├── gitlab
  │   └── my-organisation3
  │       ├── repo-3
  │       └── ...
  ├── bitbucket
  │   └── my-organisation4
  │       ├── repo-4
  │       └── ...
  ...

• ~/.gitconfig

  [commit]
  gpgsign = true
  
  [includeIf "gitdir:~/Projects/github/my-organisation1/"]
  path = ~/.gitconfig-github-my-organisation1
  
  [includeIf "gitdir:~/Projects/gitlab/my-organisation3/"]
  path = ~/.gitconfig-gitlab-my-organisation3

• ~/.gitconfig-github-my-organisation1

  [user]
  email = first.last@organisation1.com
  name = your-github-username
  signingkey = your GPG key ID
  
  [url "ssh://git@org1-github/umg/"]
  insteadOf = git@github.com:org1/

• ~/.gitconfig-gitlab-my-organisation3

  [user]
  email = first.last@organisation3.com
  name = your-gitlab-username
  signingkey = your GPG key ID
  
  [url "ssh://git@org3-gitlab/umg/"]
  insteadOf = git@gitlab.com:org3/

1. Make sure everything works by cloning some repositories using git ssh protocol

1. Read git config variables from respective paths

   $ cd ~/Projects/github/my-organisation1/repo-1 on main
   $ git config --show-origin --get user.name
   
   file:~/.gitconfig-github-my-organisation1 your-github-username

   $ cd ~/Projects/gitlab/my-organisation3/repo-3 on main
   $ git config --show-origin --get user.name
   
   file:~/.gitconfig-gitlab-my-organisation3 your-gitlab-username

2. If you get the error: gpg failed to sign the data try running $ export GPG_TTY=$(tty) before committing and add it to your ~/.zshrc config if it helped

   $ echo 'export GPG_TTY=$(tty)' >> ~/.zshrc
   $ source ~/.zshrc

3. Check ssh auth log what is happening under the hood

   $ ssh -Tv git@github.com