Pushing to GitHub using a different user over https
<p>I'm trying to push a new repo to Github on a machine that isn't mine. However, I'm getting the following error:</p>

<pre><code>user (master) sample_app $ git push -u origin master
remote: Permission to ME/sampleapp.git denied to NOTMYUSERNAME.
fatal: unable to access 'https://github.com/ME/sampleapp.git/': The requested URL returned error: 403
</code></pre>

<p>Why isn't it prompting me for my username and password? It is over https?</p>

<p>edit:
I've tried editing the global gitconfig file to remove the old username. But there seems to be no mention of 'NOTMYUSERNAME' in there.</p>