Allow retrieval of a commit message

c_src/commit.c

@@ -137,3 +137,22 @@ geef_commit_create(ErlNifEnv *env, int argc, const ERL_NIF_TERM argv[])
 
 	return enif_make_tuple2(env, atoms.ok, enif_make_binary(env, &bin));
 }
+
+ERL_NIF_TERM
+geef_commit_message(ErlNifEnv *env, int argc, const ERL_NIF_TERM argv[])
+{
+	ErlNifBinary bin;
+	geef_object *obj, *tree;
+	const char *msg;
+
+	if (!enif_get_resource(env, argv[0], geef_object_type, (void **) &obj))
+		return enif_make_badarg(env);
+
+	tree = enif_alloc_resource(geef_object_type, sizeof(geef_object));
+
+	msg = git_commit_message((git_commit *) obj->obj);
+	if (geef_string_to_bin(&bin, msg) < 0)
+		return geef_error(env);
+
+	return enif_make_tuple2(env, atoms.ok, enif_make_binary(env, &bin));
+}

c_src/commit.h

@@ -4,4 +4,5 @@
 ERL_NIF_TERM geef_commit_tree_id(ErlNifEnv *env, int argc, const ERL_NIF_TERM argv[]);
 ERL_NIF_TERM geef_commit_tree(ErlNifEnv *env, int argc, const ERL_NIF_TERM argv[]);
 ERL_NIF_TERM geef_commit_create(ErlNifEnv *env, int argc, const ERL_NIF_TERM argv[]);
+ERL_NIF_TERM geef_commit_message(ErlNifEnv *env, int argc, const ERL_NIF_TERM argv[]);
 #endif

c_src/geef.c

@@ -192,6 +192,7 @@ static ErlNifFunc geef_funcs[] =
 	{"commit_tree", 1, geef_commit_tree},
 	{"commit_tree_id", 1, geef_commit_tree_id},
 	{"commit_create",  8, geef_commit_create},
+	{"commit_message", 1, geef_commit_message},
 	{"tree_bypath", 2, geef_tree_bypath},
 	{"tree_nth",     2, geef_tree_nth},
 	{"tree_count",   1, geef_tree_count},

lib/geef/commit.ex

@@ -31,4 +31,12 @@ defmodule Geef.Commit do
     :geef_commit.create(repo, Signature.to_record(author), Signature.to_record(committer), message, tree, parents, opts)
   end
 
+  @spec message(t) :: {:ok, String.t} | {:error, term}
+  def message(%Object{type: :commit, handle: handle}) do
+    :geef_nif.commit_message(handle)
+  end
+
+  @spec message!(t) :: String.t
+  def message!(commit), do: message(commit) |> Geef.assert_ok
+
 end

src/geef_commit.erl

@@ -1,6 +1,7 @@
 -module(geef_commit).
 -export([tree_id/1, tree/1, lookup/2]).
 -export([create/5, create/6, create/7]).
+-export([message/1]).
 
 -include("geef_records.hrl").
 
@@ -53,3 +54,7 @@ create(Repo, Person = #geef_signature{}, Message, Tree, Parents, Opts) ->
 
 create(Repo, Person = #geef_signature{}, Message, Tree, Parents) ->
     create(Repo, Person, Person, Message, Tree, Parents, []).
+
+-spec message(commit()) -> {ok, binary()} | {error, term()}.
+message(#geef_object{type=commit,handle=Handle}) ->
+    geef_nif:commit_message(Handle).

src/geef_nif.erl

@@ -115,6 +115,10 @@ commit_tree(_Handle) ->
 commit_create(_RepoHandle, _Ref, _Author, _Committer, _Encoding, _Message, _Tree, _Parents) ->
     ?NIF_FN.
 
+-spec commit_message(term) -> binary().
+commit_message(_CommitHandle) ->
+    ?NIF_FN.
+
 -spec tree_bypath(term, iolist()) -> term().
 tree_bypath(_TreeHandle, _Path) ->
     nif_error(?LINE).

test/repo_test.erl

@@ -7,7 +7,7 @@ repo_test_() ->
     {foreach, fun start/0, fun stop/1, [fun bare_test/1, fun odb_write_test/1,
 					fun ref_test/1, fun index_add_test/1,
 					fun ref_iter_test/1, fun revparse_test/1,
-					fun commit_create_test/1]}.
+					fun commit_create_test/1, fun commit_message_test/1]}.
 
 start() ->
     {A, B, C} = now(),
@@ -104,6 +104,13 @@ commit_create_test(Repo) ->
     Resp = geef_commit:create(Repo, Sig, Message, TreeId, []),
     [?_assertMatch({ok, CommitId}, Resp)].
 
+commit_message_test(Repo) ->
+    commit_create_test(Repo),
+    CommitId = geef_oid:parse("bf968373f95f8fed2a24f9d25ebf06521359c6bc"),
+    {ok, Commit} = geef_commit:lookup(Repo, CommitId),
+    Resp = geef_commit:message(Commit),
+    [?_assertMatch({ok, <<"Commit message">>}, Resp)].
+
 rm_r(Path) ->
     case filelib:is_dir(Path) of
 	false ->