Auto merge of #1043 - RalfJung:cache, r=RalfJung

Cache rustup-toolchain-install-master again

We temporarily disabled the cache just to get it updated.

.appveyor.yml

@@ -28,10 +28,9 @@ install:
     - set PATH=%USERPROFILE%\.cargo\bin;%PATH%
     - rustup default stable
     - rustup uninstall beta
-    - rustup component remove rust-docs & exit 0
     - rustup update
     # Install "master" toolchain
-    - cargo install rustup-toolchain-install-master -f
+    - cargo install rustup-toolchain-install-master & exit 0
     # We need to install cargo here as well or else the DLL search path inside `cargo run`
     # will be for the wrong toolchain. (On Unix, `./miri` takes care of this, but not here.)
     - rustup-toolchain-install-master -f -n master %RUSTC_HASH% -c rust-src -c rustc-dev -c cargo

.travis.yml

@@ -35,10 +35,9 @@ before_script:
 - export PATH=$HOME/.cargo/bin:$PATH
 - rustup default stable
 - rustup uninstall beta
-- rustup component remove rust-docs || echo "rust-docs already gone"
 - rustup update
 # Install "master" toolchain
-- cargo install rustup-toolchain-install-master -f
+- cargo install rustup-toolchain-install-master || echo "rustup-toolchain-install-master already installed"
 - travis_retry rustup-toolchain-install-master -f -n master $RUSTC_HASH -c rust-src -c rustc-dev
 - rustup default master
 - rustc --version

src/bin/cargo-miri.rs

@@ -6,6 +6,8 @@
 use std::process::Command;
 use std::ops::Not;
 
+const XARGO_MIN_VERSION: (u32, u32, u32) = (0, 3, 17);
+
 const CARGO_MIRI_HELP: &str = r#"Interprets bin crates and tests in Miri
 
 Usage:
@@ -258,7 +260,7 @@ fn setup(ask_user: bool) {
     }
 
     // First, we need xargo.
-    if xargo_version().map_or(true, |v| v < (0, 3, 16)) {
+    if xargo_version().map_or(true, |v| v < XARGO_MIN_VERSION) {
         if std::env::var("XARGO").is_ok() {
             // The user manually gave us a xargo binary; don't do anything automatically.
             show_error(format!("Your xargo is too old; please upgrade to the latest version"))