Concatenating mp4 video files

I recently shot a recital with my Sony A7. While it’s a wonderful camera for stills and it produces some excellent video too, cameras like this are not meant for continuous video recording. There are limitations that are imposed by compression algorithm licensing requirements. And, it seems, there are limits that are imposed by thermal issues inside the camera. To make a long story short, my A7 ended up giving me two video files instead of one for this event.