Is there a way to have a local version of a header file?

for an embedded project built inside the Arduino IDE, (alternate firmware for a home automation project) there is a need to set a number of parameters that we really don't want in the main repo (wifi network IDs/passwords)

right now, we have these things set as #defines in a header file.

We need to distribute a base version of this file for new people to get started.

Is there any way to have git define a file in such a way that if it doesn't exist in the worktree it gets populated, but if it does exist it doesn't get overwritten? (as I type this, I'm thinking a trigger may work, but we need it to work on Linux, Windows and OSX)

Any thoughts on a sane way to handle this situation?

David Lang