Introduce git_remote_{fetch,push}_refspecs() to get a list of refspecs
from the remote and rename the refspec-adding functions to a less
silly name.
Use this instead of the vector index hacks in the tests.
A remote can have a multitude of refspecs. Up to now our git_remote's
have supported a single one for each fetch and push out of simplicity
to get something working.
Let the remotes and internal code know about multiple remotes and get
the tests passing with them.
Instead of setting a refspec, the external users can clear all and add
refspecs. This should be enough for most uses, though we're still
missing a querying function.
Return the size we'd need to write to instead of simply an
error. Split the function into two to be used later by the upstream
configuration functions.
The new tests were not taking core.filemode into account when
testing file modes after repo initialization. Fixed that and some
other Windows warnings that have crept in.
