Add geef_commit:tree_id

src/geef_commit.erl

@@ -0,0 +1,9 @@
+-module(geef_commit).
+-export([tree_id/1]).
+
+-include("geef_records.hrl").
+
+-spec tree_id(object()) -> oid().
+tree_id(#object{type=commit,handle=Handle}) ->
+    Oid = geef:commit_tree_id(Handle),
+    #oid{oid=Oid}.