Answer by misraX for Build Docker image from GitHub repository

detecting content type for remoteunsupported Content-Type "text/html; charset=utf-8"" Are you sure that you passed the right url ? If in this case you want the Dockerfile it will be in: https://raw.githubusercontent.com/Abdul-Rehman-yousaf/testing/master/Dockerfile

You can make a simple http request using wget to make sure that you are passing the right url:

wget https://raw.githubusercontent.com/Abdul-Rehman yousaf/testing/master/Dockerfile

so It seems that your are passing a wrong url, another way is to clone the repo and pass the code to the Dockerfile and it will follow it's content process by copying the desired file or folders to the container and so on....