mv std libs to library/

library/rustc-std-workspace-core/README.md

@@ -0,0 +1,29 @@
+# The `rustc-std-workspace-core` crate
+
+This crate is a shim and empty crate which simply depends on `libcore` and
+reexports all of its contents. The crate is the crux of empowering the standard
+library to depend on crates from crates.io
+
+Crates on crates.io that the standard library depend on the
+`rustc-std-workspace-core` crate from crates.io. On crates.io, however, this
+crate is empty. We use `[patch]` to override it to this crate in this
+repository. As a result, crates on crates.io will draw a dependency edge to
+`libcore`, the version defined in this repository. That should draw all the
+dependency edges to ensure Cargo builds crates successfully!
+
+Note that crates on crates.io need to depend on this crate with the name `core`
+for everything to work correctly. To do that they can use:
+
+```toml
+core = { version = "1.0.0", optional = true, package = 'rustc-std-workspace-core' }
+```
+
+Through the use of the `package` key the crate is renamed to `core`, meaning
+it'll look like
+
+```
+--extern core=.../librustc_std_workspace_core-XXXXXXX.rlib
+```
+
+when Cargo invokes the compiler, satisfying the implicit `extern crate core`
+directive injected by the compiler.