set curl options in libnetcdf via NC_rcfile_insert

[visr]

Not working yet, but hopefully we can get there to fix #173.

I searched the netcdf-c repository and found ocset_curlopt, which seems to do just what we need.

However it needs a OCstate object. If I'm reading things right this can be created using ocopen. That function does need a url argument, and I don't know what that should be. I put in an empty string for now.

When I run this, it crashes on calling ocopen, with

drc.c:80: ncrc_setrchome: Assertion `ncrc_globalstate && ncrc_globalstate->home' failed.

I don't understand this error though. This is the code:
https://github.com/Unidata/netcdf-c/blob/main/libdispatch/drc.c#L112-L123

But I don't see where home would be set here.
https://github.com/Unidata/netcdf-c/blob/c147bdd7b6032192b1738c6445e9ed370e14db5c/libsrc4/nc4internal.c#L2098-L2123

Ah and these seem like relevant environment variables:

/* getenv() keys */
#define NCRCENVIGNORE "NCRCENV_IGNORE"
#define NCRCENVRC "NCRCENV_RC"
#define NCRCENVHOME "NCRCENV_HOME"

This is where I got stuck, not sure how to proceed, or if I'm going about this right.

[Alexander-Barth]

Thanks a lot for your help! I am merged this as we have NetCDF_jll v400.802.103+0 with the required patch now.

[visr]

Oh that's great! Before releasing, it would be good to remove the println, and the NC_rclookup from __init__, as well as those comment lines.

[Alexander-Barth]

Yes, sure! Already done!