It would be nice if we can manage a repo that request support from other repo. For example, if you have repo A and hope to use repo B in A, and you hope to get updated with B. Simply use submodules!
First add from remote:
git submodule add https://github.com/user/repoB
git commit -am 'Add submodule B'
git push origin master
Done.
Clone
If you hope to clone A with submodule B:
git clone https://github.com/user/repoA
git submodule init
git submodule update
Or simply:
git clone --recurse-submodules https://github.com/user/repoA
Update
If submodule B has been upgraded by the owner, we could simply update A with this modification by:
cd B
git fetch
git merge origin master