Add geef_commit:tree_id

c_src/commit.c

@@ -0,0 +1,24 @@
+#include "geef.h"
+#include "repository.h"
+#include "object.h"
+#include "oid.h"
+#include <string.h>
+#include <git2.h>
+
+ERL_NIF_TERM
+geef_commit_tree_id(ErlNifEnv *env, int argc, const ERL_NIF_TERM argv[])
+{
+	const git_oid *id;
+	geef_object *obj;
+	ErlNifBinary bin;
+
+	if (!enif_get_resource(env, argv[0], geef_object_type, (void **) &obj))
+		return enif_make_badarg(env);
+
+	id = git_commit_tree_id((git_commit *) obj->obj);
+
+	if (geef_oid_bin(&bin, id) < 0)
+		return atoms.error;
+
+	return enif_make_binary(env, &bin);
+}