I don't remember specifics, but I had previously noticed that Geany treats the command line differently when opening files in a new instance vs opening files in an already open instance so that some combinations of parameters and files would behave differently. I believe the cause is differences between code in `socket.c` and elsewhere.
Assuming the new behavior described in this issue is not intentional, would it make sense to unify command-line handling generally? For instance, upon starting a new instance of Geany, `socket.c` could be used to handled opening all files passed through the command line.