Following the cleanup from libgit2, let's not use 'oid' unless we mean
the name of the data type. In the other cases, we mean an identifier,
hence the name 'id'.
The library stores error information in thread-local storage, which
means we need to make sure that the Go runtime doesn't switch OS
threads between the time we call a function and th time we attempt to
retrieve the error information.
Jesse Ezell
Jesper Hansen
Carlos Martín Nieto