title: dotnet restore keeps using local project instead of nuget package
body: <p>I have a .NET-core project in Visual Studio 2015. In it, I used a Nuget package, but after finding a bug in the package, I checked out its source code and included the library project into my solution to debug the issue. After successfully resolving the problem I sent the fix upstream, it was accepted and a new Nuget package version was released. So I went, removed the library project from my solution and intended to update the package to the fixed version to continue working on my project. Visual Studio Nuget Package Manager found the new version and everything seemed fine for a while.</p>
  
  <p>However, it did not work. Every time I try to update or reinstall the package, <em>the library project reappears in my solution</em> instead of just going to the nuget package dependencies. (Obviously, it still contains my checked-out version instead of the current nuget package version, so the NU1007 warning appears – dependency specified was different than what it ended up with.)</p>
  
  <p>I have deleted all user/temporary files in the project, I have deleted the <code>project.lock.json</code> file. Using a global file search, there is not a single appearance of the file path to the library project (its source code was checked out outside the main project’s directory) in any file under my project’s directory. Then I run <code>dotnet restore</code>, it does not say anything interesting, but it creates the <code>project.lock.json</code> file, and inside, it adds the old version of the package as <code>"type": "project"</code> with <code>path</code> going to its <code>project.json</code> and <code>msbuildProject</code> going to its xproj files in a completely different directory.</p>
  
  <p>Where does <code>dotnet</code> remember/find the path? Should it be doing this? What can I do to stop it from doing this and instead start using standard Nuget package source again?</p>