Recently, I created a tool that convert postgis directly to .osm file. It is simple to use. It is working on Linux Debian, but I’m not sure about others Operating Systems.
So far, it has some limitation as described in the section “To-do”, but I plan to improve the code.
Check it out on GitHub - santamariense/postgis_to_osm: postgis_to_osm converts a PostgreSQL + PostGIS table into an .osm file.