From b684645ead29b00e42d23c6ae87b7c6a14947139 Mon Sep 17 00:00:00 2001
From: EdmondFrank <edmomdfrank@yahoo.com>
Date: Sat, 22 Oct 2022 21:24:20 +0800
Subject: [PATCH] Trying to fix a non-existent HEAD

---
 apps/gitrekt/c_src/geef.c             |  1 +
 apps/gitrekt/c_src/repository.c       | 26 +++++++++++++++++++++++++-
 apps/gitrekt/c_src/repository.h       |  1 +
 apps/gitrekt/lib/gitrekt/git.ex       |  8 ++++++++
 apps/gitrekt/lib/gitrekt/git_agent.ex | 11 ++++++++++-
 5 files changed, 45 insertions(+), 2 deletions(-)

diff --git a/apps/gitrekt/c_src/geef.c b/apps/gitrekt/c_src/geef.c
index 60b99d01..65e5da8c 100644
--- a/apps/gitrekt/c_src/geef.c
+++ b/apps/gitrekt/c_src/geef.c
@@ -313,6 +313,7 @@ static ErlNifFunc geef_funcs[] =
 	{"repository_get_odb", 1, geef_repository_odb, 0},
 	{"repository_get_index", 1, geef_repository_index, 0},
 	{"repository_get_config", 1, geef_repository_config, 0},
+        {"repository_set_head", 2, geef_repository_set_head, 0},
 	{"odb_object_hash", 2, geef_odb_hash, 0},
 	{"odb_object_exists?", 2, geef_odb_exists, 0},
 	{"odb_read", 2, geef_odb_read, 0},
diff --git a/apps/gitrekt/c_src/repository.c b/apps/gitrekt/c_src/repository.c
index da901a62..e8163d99 100644
--- a/apps/gitrekt/c_src/repository.c
+++ b/apps/gitrekt/c_src/repository.c
@@ -238,4 +238,28 @@ geef_repository_index(ErlNifEnv *env, int argc, const ERL_NIF_TERM argv[])
 	enif_release_resource(index);
 
 	return enif_make_tuple2(env, atoms.ok, term_index);
-}
\ No newline at end of file
+}
+
+ERL_NIF_TERM
+geef_repository_set_head(ErlNifEnv *env, int argc, const ERL_NIF_TERM argv[])
+{
+	int error;
+	geef_repository *repo;
+        ErlNifBinary bin;
+
+	if (!enif_get_resource(env, argv[0], geef_repository_type, (void **)&repo))
+                return enif_make_badarg(env);
+
+	if (!enif_inspect_binary(env, argv[1], &bin))
+                return enif_make_badarg(env);
+
+        if (!geef_terminate_binary(&bin))
+                return geef_oom(env);
+
+        error = git_repository_set_head(repo->repo, (char *)bin.data);
+        enif_release_binary(&bin);
+        if (error < 0)
+            return geef_error_struct(env, error);
+
+	return atoms.ok;
+}
diff --git a/apps/gitrekt/c_src/repository.h b/apps/gitrekt/c_src/repository.h
index 8d8fbb2e..c317f45b 100644
--- a/apps/gitrekt/c_src/repository.h
+++ b/apps/gitrekt/c_src/repository.h
@@ -16,6 +16,7 @@ ERL_NIF_TERM geef_repository_is_empty(ErlNifEnv *env, int argc, const ERL_NIF_TE
 ERL_NIF_TERM geef_repository_odb(ErlNifEnv *env, int argc, const ERL_NIF_TERM argv[]);
 ERL_NIF_TERM geef_repository_index(ErlNifEnv *env, int argc, const ERL_NIF_TERM argv[]);
 ERL_NIF_TERM geef_repository_config(ErlNifEnv *env, int argc, const ERL_NIF_TERM argv[]);
+ERL_NIF_TERM geef_repository_set_head(ErlNifEnv *env, int argc, const ERL_NIF_TERM argv[]);
 
 void geef_repository_free(ErlNifEnv *env, void *cd);
 
diff --git a/apps/gitrekt/lib/gitrekt/git.ex b/apps/gitrekt/lib/gitrekt/git.ex
index 192cfed0..f0363286 100644
--- a/apps/gitrekt/lib/gitrekt/git.ex
+++ b/apps/gitrekt/lib/gitrekt/git.ex
@@ -379,6 +379,14 @@ defmodule GitRekt.Git do
     raise Code.LoadError, file: nif_path() <> ".so"
   end
 
+  @doc """
+  Make the `repo` HEAD point to the specified reference.
+  """
+  @spec repository_set_head(repo, binary) :: :ok | {:error, term}
+  def repository_set_head(_repo, _refname) do
+    raise Code.LoadError, file: nif_path() <> ".so"
+  end
+
   @doc """
   Initializes a new repository at the given `path`.
   """
diff --git a/apps/gitrekt/lib/gitrekt/git_agent.ex b/apps/gitrekt/lib/gitrekt/git_agent.ex
index f69e44b6..d98b32a5 100644
--- a/apps/gitrekt/lib/gitrekt/git_agent.ex
+++ b/apps/gitrekt/lib/gitrekt/git_agent.ex
@@ -755,7 +755,16 @@ defmodule GitRekt.GitAgent do
       {:ok, name, shorthand, oid} ->
         {:ok, resolve_reference({name, shorthand, :oid, oid})}
       {:error, reason} ->
-        {:error, reason}
+        case Git.reference_stream(handle, "refs/heads/*") do
+          {:ok, stream} ->
+            with %GitRef{name: name} =
+              ref <- Enum.at(Stream.map(stream, &resolve_reference_peel!(&1, :undefined, handle)), 0),
+                 :ok <- Git.repository_set_head(handle, "refs/heads/#{name}") do
+              {:ok, ref}
+            end || {:error, reason}
+          {:error, reason} ->
+            {:error, reason}
+        end
     end
   end