dh-cargo generating empty/invalid X-Cargo-Built-Using fields

[Steve Beattie]

dh-cargo as of 0.30ubuntu1 is generating not well formatted X-Cargo-Built-Using: tag entries. Two examples of this are:

- helvum in mantic and noble, which apt show contains:

  Homepage: https://gitlab.freedesktop.org/ryuukyu/helvum
  X-Cargo-Built-Using:
   ,
  Download-Size: 365 kB

- oxigraph-server in noble, which apt show contains:

  Homepage: https://github.com/oxigraph/oxigraph
  X-Cargo-Built-Using:
    (= ), rust-adler (= 1.0.2-2), rust-aho-corasick (= 1.1.2-1), [rest of build dependencies elided]

I'm assuming these are not intentional, and they cause tooling that parses these entries to be more complex.

[Simon Chopin (schopin)]

Those are not dh-cargo bugs but helvum and oxigraph-server bugs, as they vendor a version of dh-cargo in debian/dh-cargo for some reason.

[Jeremy Bícha (jbicha)]

Jonas vendors dh-cargo for all his Rust apps and crates.

Is it possible to get Ubuntu's custom changes into Debian's dh-cargo? Then we can ask Jonas to update his vendored copy.

[Jeremy Bícha (jbicha)]

The original bug was fixed in helvum but there's still this:

dpkg-gencontrol: warning: Static-Built-Using field of package helvum: substitution variable ${cargo:Static-Built-Using} used, but is not defined

https://bugs.launchpad.net/ubuntu/+source/helvum/0.5.1+20240328-1

This is also affecting https://launchpad.net/ubuntu/+source/railway-gtk/2.4.0-3