I am an engineering student who spends most of his spare time watching TV rather than coding. So basically I have zero experience with any kind of version control system. My
If you wish to update several git repositories in one command - i suggest that you read a little bit on repo.
About updating the repository, you can do it by:
git fetch git rebase origin/master
OR
git pull --rebase
For more information about using GIT you can take a look on my GIT beginners guide