Try:
public static void gitPull()
{
var startInfo = new System.Diagnostics.ProcessStartInfo
{
UseShellExecute = false,
RedirectStandardOutput = true,
FileName = "CMD.exe",
Arguments = @"/c cd d:\GIT\proj1\ & git pull master",
});
var process = System.Diagnostics.Process.Start(startInfo);
string output = process.StandardOutput.ReadToEnd();
Console.WriteLine(output);
process.WaitForExit();
}