Add ref shorthand function

lib/geef/reference.ex

@@ -1,5 +1,6 @@
 defrecord Geef.Reference, Record.extract(:geef_reference, from: "src/geef_records.hrl") do
   alias Geef.Repository
+  alias Geef.Reference
 
   def lookup(repo, name) do
     case :geef_ref.lookup(repo, name) do
@@ -53,4 +54,11 @@ defrecord Geef.Reference, Record.extract(:geef_reference, from: "src/geef_record
     end
   end
 
+  def shorthand(Reference[name: name]) do
+    :geef_ref.shorthand(name)
+  end
+  def shorthane(name) do
+    :geef_ref.shorthand(name)
+  end
+
 end

src/geef_ref.erl

@@ -1,6 +1,6 @@
 -module(geef_ref).
 
--export([lookup/2, resolve/1, create/4, dwim/2]).
+-export([lookup/2, resolve/1, create/4, dwim/2, shorthand/1]).
 
 -include("geef_records.hrl").
 
@@ -52,3 +52,16 @@ dwim(Repo, Name) ->
 	Err ->
 	    Err
     end.
+
+%% @doc Get the shorthand name for a particular reference
+-spec shorthand(geef_reference() | binary()) -> binary().
+shorthand(<<"refs/heads/", Rest/binary>>) ->
+    Rest;
+shorthand(<<"refs/tags/", Rest/binary>>) ->
+    Rest;
+shorthand(<<"refs/remotess/", Rest/binary>>) ->
+    Rest;
+shorthand(<<"refs/", Rest/binary>>) ->
+    Rest;
+shorthand(#geef_reference{name=Name}) ->
+    shorthand(iolist_to_binary(Name)).

test/repo_test.erl

@@ -44,7 +44,8 @@ create_ref_test(Repo) ->
     {ok, Ref0} = geef_ref:lookup(Repo, "refs/heads/branch"),
     {ok, Ref1} = geef_ref:lookup(Repo, "refs/heads/other"),
     [?_assertEqual(Ref0#geef_reference.target, Id),
-     ?_assertEqual(Ref1#geef_reference.target, <<"refs/heads/branch">>)].
+     ?_assertEqual(Ref1#geef_reference.target, <<"refs/heads/branch">>),
+     ?_assertEqual(<<"branch">>, geef_ref:shorthand(Ref0))].
 
 dwim_ref_test(Repo) ->
     odb_write_test(Repo),