Last week, I completely shifted my system to Arch Linux and during this process, I lost some config(s), settings, etc.

git config was one of them. I used to have a separate config like username, email, ssh key to use based on which project I was working on.
For example, my work projects require a different set of credentials (username, email, ssh-key) than the credentials I use on my personal projects.

I have done this before too but, after a while, I just tend to forget how to do it. This time, I am writing it in a post so that I can refer to it when required.

Steps

1. Go to the directory where you store the projects and create a.project.gitconfig with the desired credentials:

[user]    name = work-username    email = username@work-domain.com

1. Edit the user level.gitconfig present under$HOME/.gitconfig to include the following condition:

[includeIf "gitdir:ABSOLUTE_PROJECT_DIRECTORY_PATH"]    path = "ABSOLUTE_PROJECT_DIRECTORY_PATH/.project.gitconfig"

Basically, we are tellinggit:

"If you find a.git directory nested under this path then, use these set of credentials."

Verify

Now, go to a project inside the work/project-root directory and verify that the correct credentials is being used:

git config--list |grep-P"user|email"

Note (or Gotcha)

Keep in mind that this config will only be used bygit if it finds.git directory at that path or a parent.git directory.
For example:

work/|- .work.gitconfig|- project-a/   |- .git/|- project-b/   |- .git/

Now, my.work.gitconfig will be used when I am insideproject-a orproject-b but, not insidework.