rustdoc: Tracking issue for mergeable cross-crate info

[camelid]

This is a tracking issue for the RFC "Mergeable rustdoc cross-crate info" (rust-lang/rfcs#3662).

Note

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Steps

• Implement the RFC (rustdoc rfc#3662 changes under unstable flags #129337)
  • Implement the RFC in Cargo
    • rustdoc: make mergeable crate info more usable #148234
    • Add support for rustdoc mergeable cross-crate info parts cargo#16167
• Add documentation (to Rustdoc Book) -- cc @EtomicBomb
  • rustdoc: make mergeable crate info more usable #148234
• Stabilization PR (see instructions on rustc-dev-guide)

Unresolved Questions

• Consider removing --merge=shared and only allow it by not providing a --merge flag. This would allow removing the implementation of shared CCI later, once Cargo uses mergeable CCI. Mergeable rustdoc cross-crate info rfcs#3662 (comment)

Implementation history

• rustdoc rfc#3662 changes under unstable flags #129337
• modularize rustdoc's write_shared #128252
• nested aux-build in tests/rustdoc/ tests #128161
• rustdoc-search: add an integration test for CCI #148186