github-multi-account-setup

A guided bash script that walks you through setting up two GitHub accounts (personal + work) on the same Mac — with automatic profile switching based on which directory your repo lives in.

No more committing as the wrong user, no juggling credentials manually.

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What it does

Running ./setup.sh presents two options:

Option 1 — Full setup

1. Prompts for your personal and work GitHub usernames, emails, and workspace directories
2. Generates a separate ed25519 SSH key for each account
3. Adds both keys to ~/.ssh/config with unique host aliases and macOS Keychain integration
4. Creates ~/.gitconfig-personal and ~/.gitconfig-work with per-account identity and URL rewriting
5. Adds includeIf directives to your global ~/.gitconfig so git picks the right profile by directory
6. Pauses and guides you through adding each public key to the correct GitHub account
7. Tests both SSH connections and reports results

Option 2 — Assign a mounted volume to an existing profile

Maps a connected USB drive (or any mounted volume) to one of your existing profiles. Any git repo on that volume will automatically use the assigned identity — same as if it lived in the corresponding workspace directory on your Mac. Requires option 1 to have been completed first.

Existing files are backed up with a timestamp before anything is modified. The script is safe to re-run.

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Requirements

• macOS
• git and ssh

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Usage

git clone https://github.com/aldoportillo/github-multi-account-setup.git
cd github-multi-account-setup
chmod +x setup.sh encrypt-drive.sh # Optional if you plan to host repos on removable disk

Set up git profiles:

./setup.sh

On launch you'll see:

  1) Full setup — SSH keys, git profiles, and workspace directories
  2) Assign a mounted volume to an existing profile

Run option 1 first. After that, plug in a drive any time and run the script again to map it with option 2.

Reformat and encrypt a USB drive:

./encrypt-drive.sh

Detects connected external drives, reformats the selected one as APFS, and enables encryption. Run this before option 2 if you're setting up a new drive — an encrypted APFS volume is required for git to work correctly and to keep your files secure if the drive is lost.

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How it works

Directory-based identity switching

Git's includeIf "gitdir:..." directive conditionally loads a config file based on where the repo lives. The script adds these to your global ~/.gitconfig:

[includeIf "gitdir:~/Workspace/personal/"]
    path = ~/.gitconfig-personal

[includeIf "gitdir:~/Workspace/work/"]
    path = ~/.gitconfig-work

Option 2 adds the same kind of entry for any mounted volume:

[includeIf "gitdir:/Volumes/my-drive/"]
    path = ~/.gitconfig-personal

Each profile sets the correct user.name / user.email and rewrites GitHub URLs to use the account-specific SSH host alias.

SSH host aliases

~/.ssh/config maps two aliases to github.com with different identity files:

Host github.com-personal
    HostName github.com
    IdentityFile ~/.ssh/id_ed25519_personal

Host github.com-work
    HostName github.com
    IdentityFile ~/.ssh/id_ed25519_work

URL rewriting

Each gitconfig profile rewrites git@github.com: and https://github.com/ to the correct alias automatically, so standard clone URLs just work once the repo is in the right workspace.

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Cloning repos

After setup, clone into the correct workspace directory:

# Personal repos
cd ~/Workspace/personal
git clone git@github.com-personal:username/repo.git

# Work repos
cd ~/Workspace/work
git clone git@github.com-work:org/repo.git

Once cloned, git pull, git push, etc. all work normally — no alias needed after the initial clone.

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Verifying the setup

# In a personal repo
cd ~/Workspace/personal/some-repo
git config user.email   # → your personal email

# In a work repo
cd ~/Workspace/work/some-repo
git config user.email   # → your work email

cd /Volumes/my-drive/some-repo
git config user.email

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What gets created

File	Purpose
~/.ssh/id_ed25519_personal	SSH key for personal account
~/.ssh/id_ed25519_work	SSH key for work account
~/.ssh/config	Host aliases mapping each key to github.com
~/.gitconfig-personal	Personal identity + URL rewrite rules
~/.gitconfig-work	Work identity + URL rewrite rules
~/.gitconfig	Global config updated with includeIf directives

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Security

• Private keys stay on your machine in ~/.ssh/ and are never printed or stored anywhere else.
• Keys are added to the macOS Keychain so you only unlock them once per login session.
• If a key is compromised, revoke it on GitHub (Settings → SSH keys) and re-run the script to generate a new one.
• For USB drives, run ./encrypt-drive.sh to reformat as APFS Encrypted before storing repos on them — unencrypted drives expose your files and .env keys if lost.