Visual Studio 2015 Update 2 adds the new Publish button to the status bar to provide a quick and easy way to get solutions into source control:
“[The Publish button] aims to provide a quick and easy way to get solutions into source control. With this new publish compartment, choosing a source control provider and adding your solution will be achievable in as little as one click!
Out of the box, Publish will automatically wrap your solution in a Git repository and switch focus to the Sync page in Team Explorer to allow you to add a remote and publish your solution. As more providers support this feature, the Publish button will allow you to choose which source control you’d like to use for a given solution.”
If you don’t need this functionality, you can use the Hide the Publish button in the status bar of Visual Studio 2015 Update 2 extension for Visual Commander.
https://tabsstudio.com/
Making Visual Studio perfect 
That sounds unnecessary complicated. I can tolerate that button, but I certainly don’t need occasional “backup and collaborate” nag. What I do is not anywhere near publishing, and the company is using different source control system. Now I need to learn how to write Visual Studio extensions just to remove that distraction??? That button has to be removable by the settiong, and I believe it has to be off by default.
Removing the GitHub VS Extension will also remove the button — simplifying (removing things) is usually preferable to complifying…
I just did exactly that: removed GitHub extension from Visual Studio. The extension has disappeared from extension list as well as from the list of installed VS components. However, it had no effect of the “Publish” button in the status line. The button is still there and works just like before – an accidental click immediately activates Git for the current project.
Agreed, the publish button belongs in a menu and not on the status line. was a great disappointment to see it remain in update 3 but not a surprise.