Streams the file content into a collectable

lib/livebook/file_system/git.ex

@@ -116,7 +116,13 @@ defimpl Livebook.FileSystem, for: Livebook.FileSystem.Git do
 
   def write_stream_halt(_file_system, _state), do: raise("not implemented")
 
-  def read_stream_into(_file_system, _path, _collectable), do: raise("not implemented")
+  def read_stream_into(file_system, path, collectable) do
+    try do
+      Git.Client.stream_file(file_system, path, collectable)
+    rescue
+      error in File.Error -> FileSystem.Utils.posix_error(error.reason)
+    end
+  end
 
   def load(file_system, %{"hub_id" => _} = fields) do
     load(file_system, %{

lib/livebook/file_system/git/client.ex

@@ -43,7 +43,20 @@ defmodule Livebook.FileSystem.Git.Client do
     path = relative_path(path)
 
     with {:ok, git_dir} <- fetch_repository(file_system) do
-      show(git_dir, file_system.branch, path)
+      git(git_dir, ["show", "#{file_system.branch}:#{path}"])
+    end
+  end
+
+  @doc """
+  Streams the content of the given file from given repository.
+  """
+  @spec stream_file(FileSystem.Git.t(), String.t(), Collectable.t()) ::
+          {:ok, String.t()} | {:error, FileSystem.error()}
+  def stream_file(%FileSystem.Git{} = file_system, path, collectable) do
+    path = relative_path(path)
+
+    with {:ok, git_dir} <- fetch_repository(file_system) do
+      git(git_dir, ["show", "#{file_system.branch}:#{path}"], into: collectable)
     end
   end
 
@@ -90,10 +103,6 @@ defmodule Livebook.FileSystem.Git.Client do
     end
   end
 
-  defp show(git_dir, branch, path) do
-    git(git_dir, ["show", "#{branch}:#{path}"])
-  end
-
   defp rev_parse(git_dir, branch, path) do
     with {:ok, etag} <- git(git_dir, ["rev-parse", "#{branch}:#{path}"]) do
       {:ok, String.trim(etag)}