Merge commit 'refs/pull/53/head' of github.com:libgit2/git2go

On top: fix git_buf handling and rename signature

This fixes #57, #54.

Conflicts:
	git.go
	reference.go
	repository.go
	submodule.go

1 files changed, 5 insertions, 0 deletions

diff --git a/commit.go b/commit.go
index 498669e..0c64c76 100644
--- a/commit.go
+++ b/commit.go
@@ -94,6 +94,11 @@ func (v *Signature) Offset() int {
 }
 
 func (sig *Signature) toC() *C.git_signature {
+
+	if sig == nil {
+		return nil
+	}
+
 	var out *C.git_signature
 
 	name := C.CString(sig.Name)