More build-manifest docs

src/tools/build-manifest/README.md

@@ -1,7 +1,16 @@
 # build-manifest
 
-This tool generates the manifests uploaded to static.rust-lang.org and used by
-rustup. The tool is invoked by the bootstrap tool.
+This tool generates the manifests uploaded to static.rust-lang.org and used by rustup.
+You can see a full list of all manifests at <https://static.rust-lang.org/manifests.txt>.
+
+This gets called by `promote-release` <https://github.com/rust-lang/promote-release> via `x.py dist hash-and-sign`.
+
+## Adding a new component
+
+There are several steps involved here.
+1. Add a new `Step` to `dist.rs`. This should usually be named after the filename of the uploaded tarball. See https://github.com/rust-lang/rust/pull/101799/files#diff-2c56335faa24486df09ba392d8900c57e2fac4633e1f7038469bcf9ed3feb871 for an example.
+    a. If appropriate, call `tarball.is_preview(true)` for the component.
+3. Add a new `PkgType` to build-manifest. Fix all the compile errors as appropriate.
 
 ## Testing changes locally
 
@@ -9,19 +18,16 @@ In order to test the changes locally you need to have a valid dist directory
 available locally. If you don't want to build all the compiler, you can easily
 create one from the nightly artifacts with:
 
-```
-#!/bin/bash
-for cmpn in rust rustc rust-std rust-docs cargo; do
-    wget https://static.rust-lang.org/dist/${cmpn}-nightly-x86_64-unknown-linux-gnu.tar.gz
+```sh
+for component in rust rustc rust-std rust-docs cargo; do
+    wget -P build/dist https://static.rust-lang.org/dist/${component}-nightly-x86_64-unknown-linux-gnu.tar.gz
 done
 ```
 
-Then, you can generate the manifest and all the packages from `path/to/dist` to
-`path/to/output` with:
+Then, you can generate the manifest and all the packages from `build/dist` to
+`build/manifest` with:
 
+```sh
+mkdir -p build/manifest
+cargo +nightly run -p build-manifest build/dist build/manifest 1970-01-01 http://example.com nightly
 ```
-$ cargo +nightly run path/to/dist path/to/output 1970-01-01 http://example.com CHANNEL
-```
-
-Remember to replace `CHANNEL` with the channel you produced dist artifacts of
-and `VERSION` with the current Rust version.

src/tools/build-manifest/src/main.rs

@@ -1,8 +1,4 @@
-//! Build a dist manifest, hash and sign everything.
-//! This gets called by `promote-release`
-//! (https://github.com/rust-lang/rust-central-station/tree/master/promote-release)
-//! via `x.py dist hash-and-sign`; the cmdline arguments are set up
-//! by rustbuild (in `src/bootstrap/dist.rs`).
+#![doc = include_str!("../README.md")]
 
 mod checksum;
 mod manifest;