Fix artifact version/channel detection for stable

On stable, our artifacts are uploaded with the raw version number (e.g.,
1.65.0), not the channel. This adjusts our detection logic to use the
version number from src/version when we detect the stable channel.

Author: Mark-Simulacrum

src/bootstrap/config.rs

@@ -1380,21 +1380,46 @@ impl Config {
         git
     }
 
-    pub(crate) fn artifact_channel(&self, builder: &Builder<'_>, commit: &str) -> String {
-        if builder.rust_info.is_managed_git_subrepository() {
+    /// Bootstrap embeds a version number into the name of shared libraries it uploads in CI.
+    /// Return the version it would have used for the given commit.
+    pub(crate) fn artifact_version_part(&self, builder: &Builder<'_>, commit: &str) -> String {
+        let (channel, version) = if builder.rust_info.is_managed_git_subrepository() {
             let mut channel = self.git();
             channel.arg("show").arg(format!("{}:src/ci/channel", commit));
             let channel = output(&mut channel);
-            channel.trim().to_owned()
-        } else if let Ok(channel) = fs::read_to_string(builder.src.join("src/ci/channel")) {
-            channel.trim().to_owned()
+            let mut version = self.git();
+            version.arg("show").arg(format!("{}:src/version", commit));
+            let version = output(&mut version);
+            (channel.trim().to_owned(), version.trim().to_owned())
         } else {
-            let src = builder.src.display();
-            eprintln!("error: failed to determine artifact channel");
-            eprintln!(
-                "help: either use git or ensure that {src}/src/ci/channel contains the name of the channel to use"
-            );
-            panic!();
+            let channel = fs::read_to_string(builder.src.join("src/ci/channel"));
+            let version = fs::read_to_string(builder.src.join("src/version"));
+            match (channel, version) {
+                (Ok(channel), Ok(version)) => {
+                    (channel.trim().to_owned(), version.trim().to_owned())
+                }
+                (channel, version) => {
+                    let src = builder.src.display();
+                    eprintln!("error: failed to determine artifact channel and/or version");
+                    eprintln!(
+                        "help: consider using a git checkout or ensure these files are readable"
+                    );
+                    if let Err(channel) = channel {
+                        eprintln!("reading {}/src/ci/channel failed: {:?}", src, channel);
+                    }
+                    if let Err(version) = version {
+                        eprintln!("reading {}/src/version failed: {:?}", src, version);
+                    }
+                    panic!();
+                }
+            }
+        };
+
+        match channel.as_str() {
+            "stable" => version,
+            "beta" => channel,
+            "nightly" => channel,
+            other => unreachable!("{:?} is not recognized as a valid channel", other),
         }
     }
 
@@ -1637,7 +1662,7 @@ fn maybe_download_rustfmt(builder: &Builder<'_>) -> Option<PathBuf> {
 
 fn download_ci_rustc(builder: &Builder<'_>, commit: &str) {
     builder.verbose(&format!("using downloaded stage2 artifacts from CI (commit {commit})"));
-    let channel = builder.config.artifact_channel(builder, commit);
+    let version = builder.config.artifact_version_part(builder, commit);
     let host = builder.config.build.triple;
     let bin_root = builder.out.join(host).join("ci-rustc");
     let rustc_stamp = bin_root.join(".rustc-stamp");
@@ -1646,13 +1671,13 @@ fn download_ci_rustc(builder: &Builder<'_>, commit: &str) {
         if bin_root.exists() {
             t!(fs::remove_dir_all(&bin_root));
         }
-        let filename = format!("rust-std-{channel}-{host}.tar.xz");
+        let filename = format!("rust-std-{version}-{host}.tar.xz");
         let pattern = format!("rust-std-{host}");
         download_ci_component(builder, filename, &pattern, commit);
-        let filename = format!("rustc-{channel}-{host}.tar.xz");
+        let filename = format!("rustc-{version}-{host}.tar.xz");
         download_ci_component(builder, filename, "rustc", commit);
         // download-rustc doesn't need its own cargo, it can just use beta's.
-        let filename = format!("rustc-dev-{channel}-{host}.tar.xz");
+        let filename = format!("rustc-dev-{version}-{host}.tar.xz");
         download_ci_component(builder, filename, "rustc-dev", commit);
 
         builder.fix_bin_or_dylib(&bin_root.join("bin").join("rustc"));

src/bootstrap/native.rs

@@ -269,8 +269,8 @@ fn download_ci_llvm(builder: &Builder<'_>, llvm_sha: &str) {
     } else {
         &builder.config.stage0_metadata.config.artifacts_server
     };
-    let channel = builder.config.artifact_channel(builder, llvm_sha);
-    let filename = format!("rust-dev-{}-{}.tar.xz", channel, builder.build.build.triple);
+    let version = builder.config.artifact_version_part(builder, llvm_sha);
+    let filename = format!("rust-dev-{}-{}.tar.xz", version, builder.build.build.triple);
     let tarball = rustc_cache.join(&filename);
     if !tarball.exists() {
         let help_on_error = "error: failed to download llvm from ci