Extra Variables

[ghost]

Currently the variables provided through extra will be ignored by the processes in the case where I would use something that already exists, like PATH. Reasom being that the user provided extras are added last to the list.

I would suggest adding two options to this:

1. strcat to already existing varibles

2. Override already existing variables (add the user extras first)

Default behaviour being the way reproc handles it atm.

[DaanDeMeyer]

Sure, we can add REPROC_ENV_EXTEND_MERGE or so that merges environment variables with the same name. I'd be happy to review a PR that adds this

[ghost]

I'll start working on it then. 👍