This lets us see what the server (or libgit2 locally) is doing, rather
than having to stare at a non-moving screen.

Code restructured to better represent best practice when
using libgit2.

Added forgotten call to git_libgit2_shutdown() to the /examples/network/git2.c.

The signature for the reflog is not something which changes
dynamically. Almost all uses will be NULL, since we want for the
repository's default identity to be used, making it noise.

In order to allow for changing the identity, we instead provide
git_repository_set_ident() and git_repository_ident() which allow a user
to override the choice of signature.

Local transports don't have data about the size, avoid dividing by
zero in the callback.

This describes their purpose better, as we now initialize ssl and some
other global stuff in there. Calling the init function is not something
which has been optional for a while now.

This brings it in line with the rest of the lookup functions.

With opportunistic ref updates, git has introduced the concept of having
base refspecs *and* refspecs that are active for a particular fetch.

Let's start by letting the user override the refspecs for download.