How can I push to my fork from a clone of the original repo?

By default, when you clone a repository

• that resides at https://github.com/original/orirepo.git,
• whose current branch is called master,

then

• the local config of the resulting clone lists only one remote called origin, which is associated with the URL of the repository you cloned;
• the local master branch in your clone is set to track origin/master.

Therefore, if you don’t modify the config of your clone, Git interprets

git push

as

git push origin master:origin/master

In other words, git push attempts to push your local master branch to the master branch that resides on the remote repository (known by your clone as origin). However, you’re not allowed to do that, because you don’t have write access to that remote repository.

You need to

1. either redefine the origin remote to be associated with your fork, by running

   git remote set-url origin https://github.com/RemiB/myrepo.git
   

2. or, if you want to preserve the original definition of the origin remote, define a new remote (called myrepo, here) that is associated to your fork:

   git remote add myrepo https://github.com/RemiB/myrepo.git
   

   Then you should be able to push your local master branch to your fork by running

   git push myrepo master
   

   And if you want to tell Git that git push should push to myrepo instead of origin from now on, you should run

   git push -u myrepo master
   

instead.