tools: use -Zinstall-upgrade instead of a crate when unstable is enabled

Author: pietroalbini

CHANGELOG.md

@@ -19,6 +19,10 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
   instead of being cached during the workspace's initialization. It's possible
   to use the `WorkspaceBuilder::fetch_registry_index_during_builds` method to
   revert to the old behavior.
+- When the `unstable` feature flag is enabled rustwide will use Cargo's
+  `-Zinstall-upgrade` to update its tools instead of the
+  `cargo-install-upgrade` crate. This will speed up the workspace
+  initialization.
 
 ## [0.2.0] - 2019-09-06
 

src/tools/binary_crates.rs

@@ -1,5 +1,5 @@
 use crate::cmd::{Binary, Command, Runnable};
-use crate::tools::{Tool, CARGO_INSTALL_UPDATE};
+use crate::tools::Tool;
 use crate::{Toolchain, Workspace};
 use failure::Error;
 use std::path::PathBuf;
@@ -58,11 +58,25 @@ impl Tool for BinaryCrate {
         Ok(())
     }
 
+    #[cfg(not(feature = "unstable"))]
     fn update(&self, workspace: &Workspace, _fast_install: bool) -> Result<(), Error> {
-        Command::new(workspace, &CARGO_INSTALL_UPDATE)
+        Command::new(workspace, &crate::tools::CARGO_INSTALL_UPDATE)
             .args(&[self.crate_name])
             .timeout(None)
             .run()?;
         Ok(())
     }
+
+    #[cfg(feature = "unstable")]
+    fn update(&self, workspace: &Workspace, fast_install: bool) -> Result<(), Error> {
+        let mut cmd = Command::new(workspace, &Toolchain::MAIN.cargo())
+            .args(&["-Zinstall-upgrade", "install", self.crate_name])
+            .env("__CARGO_TEST_CHANNEL_OVERRIDE_DO_NOT_USE_THIS", "nightly")
+            .timeout(None);
+        if fast_install {
+            cmd = cmd.args(&["--debug"]);
+        }
+        cmd.run()?;
+        Ok(())
+    }
 }

src/tools/mod.rs

@@ -11,6 +11,7 @@ use std::path::PathBuf;
 
 pub(crate) static RUSTUP: Rustup = Rustup;
 
+#[cfg(not(feature = "unstable"))]
 pub(crate) static CARGO_INSTALL_UPDATE: BinaryCrate = BinaryCrate {
     crate_name: "cargo-update",
     binary: "cargo-install-update",
@@ -31,6 +32,7 @@ pub(crate) static GIT_CREDENTIAL_NULL: BinaryCrate = BinaryCrate {
 
 static INSTALLABLE_TOOLS: &[&dyn Tool] = &[
     &RUSTUP,
+    #[cfg(not(feature = "unstable"))]
     &CARGO_INSTALL_UPDATE,
     &RUSTUP_TOOLCHAIN_INSTALL_MASTER,
     &GIT_CREDENTIAL_NULL,