Right on time, I just finished it!

- I've been in touch with Antonio, Lzip's maintainer, for more than a
  week and now I'm confident that I have a decent understanding of the
  library.

- Your m4 suggestion didn't work.  I've included a comment.  We need to
  fix it before merging.  I'm not the right person for this job I'm
  afraid :p  Ludo?

- The convenience functions do not support multi-member archives.
  Multi-member archives are mostly useful for parallelization, but we
  don't use that in Guix, so it's OK.  Should it be required some day,
  we would need to implement it, which requires a little bit more work.
  I've documented all that.

- The implementation of lzread! is subpar because I understood a
  subtlety a bit too late.  But that's alright, it does not affect
  performance nor reliability.

- I've included 11 tests covering all your suggestions.

- I haven't strace'd the Guile process.  The code regarding ports is
  identical to zlib.scm, so it's unlikely there would be an issue in
  this area.  I have never done this before, so out of curiosity, how do
  you run a specific Guix tests without going through `make'?

Next steps? :D

-- 
Pierre Neidhardt
https://ambrevar.xyz/