Implementation: #7649
Original proposal: #6699
Documentation: https://doc.rust-lang.org/nightly/cargo/reference/unstable.html#config-include
Issues: https://github.com/rust-lang/cargo/labels/Z-config-include

Summary

Adds the include config key to include other config files.

Unresolved issues

• Should there be any restriction on the filename? Currently there isn't. I was initially considering restricting to .cargo/config-* in case we want to safely use other filenames in .cargo/ for other purposes. However, it seems like an unnatural restriction. Another restriction is that it should maybe end in .toml?
  • The team has decided on putting a restriction on allowing .toml extension only. See Tracking issue for config-include #7723 (comment)
• Inconsistent relative path behavior in configurations: Inconsistent relative path behavior between config include and other fields #15769
• Optional include supports and syntax: Tracking issue for config-include #7723 (comment).

FCP： #16284 (comment)