Recently we wanted to create a yocto cgit repository mirror onto our github which should track our changes as well as yocto git, follow below steps to create a mirror on github,
This assumes, we are cloning into poky-mirror directory on our local machine ~/Desktop/devlab/yocto and we have create a new repository named “poky” into our github account.
$ cd ~/Desktop/devlab/yocto
$ git clone --mirror git://git.yoctoproject.org/poky poky-mirror
$ cd poky-mirror/
$ git remote set-url --push origin https://github.com/lynxbee/poky
$ git push --mirror
With this, you should see a git like https://github.com/lynxbee/poky onto your github . Replace URLs as per your need.
Reference : github help