Re: [PATCH v4 3/9] checkout.[ch]: move struct declaration into *.h

Thomas Gummerer [off-list ref] writes:

We seem to have plenty of structs defined in '.c' files, if they are
only needed there.  Its use also seems to be single purpose for the
callback data, so I'm a bit puzzled how having this in a header file
instead of the .c file would be helpful?

I feel like having only the "public" part in the header file also
helps developers that are just looking for documentation of the
functions they are looking at, by having less things to go through,
that they wouldn't necessarily care about.

Yup, sounds like a sensible criterion to choose between <*.h> and
<*.c>.