bug#46967: Connection reuse for substitutes breaks with gzip

[Ludovic Courtès]

Hi!

Ludovic Courtès <ludo@gnu.org> skribis:

> This is because with ‘filtered-port’, the input port is dumped from a
> child process, not from the calling process.

I decided to take a heavy-handed solution to that problem, which is to
augment Guile-zlib with an interface for gzip compression/decompression
not restricted to file ports (‘call-with-gzip-output-port’ & co. are
restricted to file ports):

  
https://notabug.org/guile-zlib/guile-zlib/commit/b899ac2fecf91475da1eba7e7b24708ea8b5fb73

That way, we can change ‘decompressed-port’ in (guix utils) to perform
in-process decompression for ‘gzip’, like it does for zstd and lzip.

If everything goes well, I’ll cut a Guile-zlib release today and update
Guix accordingly.

Ludo’.