When I try to save a buffer back to a file:

> 
> install-packages.sh has changed since visited or saved. Save anyway?
>  (yes or no)
> 
> 
> 

I don't know why it happens, but I also see `#install-packages.sh#` exists in the same directory.

What do yes and no mean? Do they perform three way merge?

I would like to keep changes from different sources.