Test on FreeBSD is failing due to `tar entry kind 'GNUSparse' is not supported`

[rami3l]

Unfortunately, when trying to upgrade our FreeBSD runner to v15 in #4750, we have hit another regression on FreeBSD (https://bugs.freebsd.org/bugzilla/show_bug.cgi?id=286618, composefs/tar-rs#295):

  stderr:
  ====
  info: syncing channel updates for stable-x86_64-unknown-freebsd
  info: latest update on 2024-05-01 for version 1.78.0 (hash-stable-1.78.0)
  info: downloading 4 components
  error: failed to extract package: tar entry kind 'GNUSparse' is not supported
  
  ====
  
  
  thread 'suite::cli_v2::update_removed_component_toolchain' (112036) panicked at src/test/clitools.rs:197:9:
  assertion `left == right` failed
    left: Some(1)
   right: Some(0)

https://github.com/rust-lang/rustup/actions/runs/23116207400/job/67142055466?pr=4750

[ChrisDenton]

Hm, why did this regress? Haven't we always used tar-rs? Or did something change with how rust-lang/rust packages archives?

[rami3l]

@ChrisDenton I'm not pretty sure but juliaup might be on the same boat as us.

JuliaLang/juliaup#872 gives the following which is probably very interesting:

// As of this writing, the Rust `tar` library does not fully implement reading the
// POSIX.1-2001 PAX format. This is the default format used by BSD tar, and is thus
// the format of the Julia tarballs on BSD systems. There is a PR to add support for
// PAX to tar.rs: https://github.com/alexcrichton/tar-rs/pull/298, but as of this
// writing, it has not been merged. Thus we'll shell out to command line `tar` on
// FreeBSD in the meantime, and unify the approaches if/when support is available.

... although it might have something to do with our mock release server, since it doesn't look like we are not able to download anything on FreeBSD v15:

Install Rustup using ./rustup-init.sh
  + echo =========
  + echo 'Install Rustup using ./rustup-init.sh'
  + sh rustup-init.sh --default-toolchain=stable --profile=minimal -y
  info: downloading installer
  warn: It looks like you have an existing rustup settings file at:
  warn: /home/runner/work/rustup/rustup/.rustup/settings.toml
  warn: Rustup will install the default toolchain as specified in the settings file,
  warn: instead of the one inferred from the default host triple.
  info: profile set to minimal
  info: default host triple is x86_64-unknown-freebsd
  info: syncing channel updates for stable-x86_64-unknown-freebsd
  info: latest update on 2026-03-05 for version 1.94.0 (4a4ef493e 2026-03-02)
  info: downloading 3 components
  
  info: default toolchain set to stable-x86_64-unknown-freebsd
    stable-x86_64-unknown-freebsd installed - rustc 1.94.0 (4a4ef493e 2026-03-02)
  
  
  Rust is installed now. Great!

[djc]

Looks like tar-rs has been more actively recently, added a comment to

• Add support for PAX Format, Version 1.0 composefs/tar-rs#298

to see if we can get it merged.

[rami3l]

Looks like more follow-up is happening in composefs/tar-rs#457 right now?