Everything started with a clone of https://github.com/permutationlock/merge-pgn to merge PGN files with support for normal and software comments, but it eventually evolved to the point where I felt it deserved its own repository, partly because I have added more scripts to deal with PGN files, such as injecting transpositions and other things.
Go to https://github.com/olleeriksson/pgn-tools to find the new scripts.