After reading about using GIT with Visual Studio solution, I understand that it is preferable to use GIT per project, at least for project which represent a (re-usable) common library. If you have a solution with many projects specific to that solution, using only one repository could be acceptable. For common library, it appears logical to me to have one repository for it in order to be able to fix bugs in the common library from where you detect it and have only one history for all changes.
Using one GIT per common project means that you have more than one GIT repository for any solution that produce an executable that use one or more common library.
According to this: Visual Studio suggestion - Allow multiple Git repositories to be active at once, Visual Studio seems to not support many GIT repository seamlessly. (1995 request)
Does Visual Studio 2017 implement the previous suggestion and manage many GIT repository per solution? (ex: one per project for some projects and one per solution for the solution itself and all other specific projects to this solution)? In other words, does Microsoft will see and manage changes per project/GIT or do I have to works with only one GIT at the solution Level?
Just as a side one (this is not the primary question - the real question is in the previous paragraph): If Visual Studio does not allow multiple GIT repo to be active at once, wouldn't be better to stick with TFS for the moment for any development with common library?
While there has not been great support for multi repo solutions in the past, this is about to change. In Visual Studio 16.11 Preview 1, there is now a much more fully featured Git client, multiple repositories are detected and users can easily switch between them using a repository selector in the status bar.
See this blog for further information: Enhanced Productivity with Git in Visual Studio