Fix linters and address review comments

Signed-off-by: Emerson Knapp <emerson.b.knapp@gmail.com>

rosbag2_transport/include/rosbag2_transport/bag_rewrite.hpp

@@ -32,6 +32,9 @@ namespace rosbag2_transport
 /// - compress
 /// - serialization format conversion
 ///
+/// Note: If a serialization format is not specified for an output bag's RecordOptions,
+/// any topic going into it will use the serialization format of the last input with that topic.
+///
 /// \param input_options vector of settings to create Readers for bags to read messages from
 /// \param output_bags - full "recording" configuration of the bag(s) to write messages to
 ///   Each output bag will be passed messages from every input bag,

rosbag2_transport/src/rosbag2_transport/bag_rewrite.cpp

@@ -35,6 +35,7 @@ namespace
 /// Find the next chronological message from all opened input bags.
 /// Updates the next_messages queue as necessary.
 /// next_messages is needed because Reader has no "peek" interface, we cannot put a message back.
+/// Returns nullptr when all input bags have been fully read.
 std::shared_ptr<rosbag2_storage::SerializedBagMessage> get_next(
   const std::vector<std::unique_ptr<rosbag2_cpp::Reader>> & input_bags,
   std::vector<std::shared_ptr<rosbag2_storage::SerializedBagMessage>> & next_messages)

rosbag2_transport/test/rosbag2_transport/test_rewrite.cpp

@@ -14,6 +14,10 @@
 
 #include <gmock/gmock.h>
 
+#include <string>
+#include <vector>
+#include <utility>
+
 #include "rcpputils/filesystem_helper.hpp"
 #include "rosbag2_transport/bag_rewrite.hpp"
 #include "rosbag2_transport/reader_writer_factory.hpp"
@@ -72,7 +76,7 @@ class TestRewrite : public Test
   const rcpputils::fs::path output_dir_;
   std::vector<rosbag2_storage::StorageOptions> input_bags_;
   std::vector<std::pair<rosbag2_storage::StorageOptions, rosbag2_transport::RecordOptions>>
-    output_bags_;
+  output_bags_;
 };
 
 TEST_F(TestRewrite, test_noop_rewrite) {