Auto merge of #10659 - Muscraft:prestabilization-inheritance-docs, r=epage

pre-stabilization documentation for workspace inheritance

This is adding documentation for how we would like users to test workspace inheritance.

This came about from a discussion between `@epage` and I on better ways to document "pre-stabilization" features that are looking for people to test them. One of the ideas was to add some of the documentation to `unstable.md` so that it is all in one area. Having it in one area allows us to link to it so there are testing notes and documentation in one place. It also helps when posting in various places looking for testers as we can link to the nightly docs as needed. One idea was to post in TWiR [under a new table](rust-lang/this-week-in-rust#3236) and this also helps with this.

The new documentation covers
- What we are looking for from testers
- Where to give feedback
- How to test this feature
- An example port as a guide

r? `@epage`

Author: bors

src/doc/src/reference/unstable.md

@@ -1215,6 +1215,37 @@ cargo check -Z unstable-options -Z check-cfg=features,names,values
 
 * RFC: [#2906](https://github.com/rust-lang/rfcs/blob/master/text/2906-cargo-workspace-deduplicate.md)
 * Tracking Issue: [#8415](https://github.com/rust-lang/cargo/issues/8415)
+* [Status](https://github.com/rust-lang/cargo/issues/8415#issuecomment-1112618913)
+* [Example Port](https://github.com/clap-rs/clap/pull/3719)
+
+### Testing notes
+
+Target audience for testing
+* Maintainer who has a workspace
+* *(optional)* Project depends on nightly toolchain
+
+In preparing to stabilize, we are wanting to better understand
+* If there were any pain points in porting your project
+* Any errors or bugs that you found in testing
+* Performance concerns
+* Gaps in documentation
+* Thoughts on how you feel this feature will work in practice
+
+Please provide feedback on the [tracking issue](https://github.com/rust-lang/cargo/issues/8415)
+or create an issue for any bugs encountered.
+
+To get started
+1. Have a (recent) nightly version installed
+2. Place `cargo-features = ["workspace-inheritance"]` at the top of any `Cargo.toml` you 
+plan to use this feature in
+3. Create a `[workspace.package]` and `[workspace.dependencies]` in your workspace `Cargo.toml`
+4. Move any package keys or dependencies you feel should be shared between crates to their 
+respective workspace table
+5. Change any keys you want to inherit to `{key}.workspace = true` in the member `Cargo.toml`
+6. run `cargo +nightly check`
+
+An example port has been made [in this PR](https://github.com/clap-rs/clap/pull/3719) as
+a "real-life" guide.
 
 ### The `workspace.package` table