This tests the fixes for issues from #1849

When enabled, only the first parent of each commit will be queued,
enabling a simple way of using first-parent simplification.

Now that #1785 is merged, git_odb_stream_finalize_write() calculates the object id before invoking the odb backend.

This commit gives a chance to the backend to check if it already knows this object.

The GIT_MODE_TYPE macro was looking at all bits above the
permissions, but it should really just look at the top bits so
that it will give the right results for a setgid or setuid entry.

Since we're now using these macros in the tests, this was causing
a test failure on platforms that don't support setgid.

This fixes an issue checking file modes in the tests that
initialize a repo from a template directory when a symlink is
used in the template.  Also, this updates some other places where
we are examining file modes to use the new macros.

Some windows tests were failing

It seems that libgit2 is correctly applying the umask when
initializing a repository from a template and when creating new
directories during checkout, but the test suite is not accounting
for possible variations due to the umask.  This updates that so
that the test suite will work regardless of the umask.

Ensure that we apply splits to rewrites, even if we're not
interested in examining it closely for rename/copy detection.

In keeping with core git, status should not display rewrites,
it should simply show files as "modified".

In order to be loaded, a remote needs to be configured with at least a `url` or a `pushurl`.

ENOTFOUND will be returned when trying to git_remote_load() a remote with neither of these entries defined.

238b7614 introduced a test for posix behaviour, but on FreeBSD some
of the structs and constants used aren't defined in <arpa/inet.h>.
Include the appropriate headers to get the tests working again on
FreeBSD.