PowerShellInvoke.cs

string directory = ""; // directory of the git repository

using (PowerShell powershell = PowerShell.Create()) {
    // this changes from the user folder that PowerShell starts up with to your git repository
    powershell.AddScript($"cd {directory}");

    powershell.AddScript(@"git init");
    powershell.AddScript(@"git add *");
    powershell.AddScript(@"git commit -m 'git commit from PowerShell in C#'");
    powershell.AddScript(@"git push");

    Collection<PSObject> results = powershell.Invoke();
}