Don't load refspecs eagerly
Don't load refspecs eagerly

If the user never asks for the refspecs, we should not spend the time and memory
to load them into managed memory.

Zoxive/libgit2sharp,red-gate/libgit2sharp,Zoxive/libgit2sharp,libgit2/libgit2sharp,red-gate/libgit2sharp,PKRoma/libgit2sharp