GIT: Use different config (git username / gmail or ssh keys) in different projects ​

Background ​

When using Git, we often configure some basic configuration items, such as the user name (user.name) and the email (user.email). If they are not configured, the first time you use Git to commit code will report an error:

Make sure you configure your 'user.email' and 'user.name' in git

We can fix this by using the git config command to set the values.

git config --global user.name "Tinymemo"
git config --global user.email "[email protected]"

This command actually writes two configuration items to the global configuration file: user.name and user.email. We can try opening the configuration file (usually located at ~/.gitconfig or C:\Users\<username>\.gitconfig):

[user]
        name = Tinymemo
        email = tinymemo

If we don't run the command with --global option, the configuration file will be written to the current directory, usually located at .git/config.

Use different config in different projects ​

When we want to participate in projects with different identities, we need to use different configuration in each project. But we don't want to write separate configuration in each project, because we had to use the global configuration if the project doesn't have a configuration. So we need a better way.

Fortunately, Git provides the includeIf directive, which can be used to specify different configuration for different paths.

Assume we have the following two paths:

• ~/work the corresponding user name and email is Tinymemo / [email protected]
• ~/hobby the corresponding user name and email is Tinymemo / [email protected]

First, we create two separate configuration files:

~/.gitconfig-work：

[user]
        name = Tinymemo
        email = [email protected]

~/.gitconfig-hobby：

[user]
        name = Tinymemo
        email = [email protected]

Then we add the following lines to the global configuration file ~/.gitconfig, please notice the last slash in the path:

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

Then we can verify in the corresponding directory of the project:

# ~/work/project1
git config user.name // Tinymemo
git config user.email // [email protected]

# ~/hobby/project2
git config user.name // Tinymemo
git config user.email // [email protected]

Note: you must run git config command in the project directory, otherwise it will use the global configuration.

So we can make it easy to use different configuration in different projects.

Use different config for public/private key ​

Then configuration above makes it easy to use different username and email for different projects, but we also want to use different SSH public/private key for different projects in some cases.

First, we need to create a new public key. If we have a public key already, we can skip this step.

cd ~/.ssh
ssh-keygen -t rsa

Please note the file name, can not be the default id_rsa name, otherwise it will conflict with the existing public key.

Enter file in which to save the key (/Users/tinymemo/.ssh/id_rsa): id_rsa_hobby

Just press enter all the way.

Then we can add a new configuration item to the configuration file, to specify the new public key for the ssh command:

[core]
    sshCommand = "ssh -i ~/.ssh/id_rsa_hobby -F /dev/null"

After this, we can use different public/private keys for different projects:

Summary ​

By using [includeIf] directive in global configuration, we can easily use different username, email and public/private key for different projects in different directories.