Per-directory git config

Pantos May 04, 2024 #git #ssh

Multiple SSH keys

To generate a new key for each account or service:

ssh-keygen -t ed25519 -C "foo@blarb.org" -f "~/.ssh/foo"
ssh-keygen -t ed25519 -C "bar@blubb.org" -f "~/.ssh/bar"

If the keys are used for accounts in different services like github or bitbucket, we can have each service use a different ssh config.

Add to ~/.ssh/config:

Host github.com
    Hostname github.com
    IdentityFile ~/.ssh/foo
    IdentitiesOnly yes

Host bitbucket.org
    Hostname bitbucket.org
    IdentityFile ~/.ssh/bar
    IdentitiesOnly yes

Then each service will have a certain SSH key assigned, system-wide. So far so good, but this won't work for different accounts on the same service.

This can be tackled in a different way though, but let's first have alook at...

Multiple git identities

Let's assume we have different git identities (i.e. name/email) for each of the services, and we want git to automatically choose the right one.

Create two parent directories that each contains our repos for the according service, e.g.:
```
mkdir ~/github
mkdir ~/bitbucket
```

Add to ~/.gitconfig:

[includeIf "gitdir:~/github"]
    path = ~/github/.gitconfig
[includeIf "gitdir:~/bitbucket"]
    path = ~/bitbucket/.gitconfig

Create ~/github/.gitconfig:

[user]
    email = foo@blarb.org
    name = Foo

Create ~/bitbucket/.gitconfig:

[user]
    email = bar@blubb.org
    name = Bar

With this, git will pick the an identity, depending on the parent directory that the git repo is in. This will not be system-wide, so if we want to add new identities, we will have to create additional parent dirs and add new includeIf entries.

Different SSH keys depending on parent directory

Instead of using the SSH config file, we can use the different git config files in the respective parent directories to pick the right SSH key.

Add to ~/github/.gitconfig:

[core]
    sshCommand = ssh -i ~/.ssh/foo

Add to ~/bitbucket/.gitconfig:

[core]
    sshCommand = ssh -i ~/.ssh/bar

This can even be used for different git accounts on the same service. Depending on the parent directory, a certain author, email and ssh key will be used.