GOAL: include EWF into your own git repository
For instance, let's put it under lib/EWF

  git remote add -f _ewf https://github.com/EiffelWebFramework/EWF.git
  git merge --squash -s ours --no-commit _ewf/master
  git read-tree --prefix=lib/EWF/ -u _ewf/master
  git commit -m "Imported EWF into subtree lib/EWF/"

Then to update lib/EWF
  git pull -X subtree=lib/EWF _ewf master

From another git clone, reconnect this "import"
  git remote add -f _ewf https://github.com/EiffelWebFramework/EWF.git
  git merge -s ours --no-commit --squash _ewf/master
  and then update lib/EWF as described before