Make cargo-the-binary version the same as the Rust version

Closes #4211

Author: matklad

src/cargo/lib.rs

@@ -72,9 +72,9 @@ pub struct CfgInfo {
 }
 
 pub struct VersionInfo {
-    pub major: String,
-    pub minor: String,
-    pub patch: String,
+    pub major: u8,
+    pub minor: u8,
+    pub patch: u8,
     pub pre_release: Option<String>,
     // Information that's only available when we were built with
     // configure/make, rather than cargo itself.
@@ -192,12 +192,28 @@ fn handle_cause(cargo_err: &Error, shell: &mut Shell) -> bool {
 }
 
 pub fn version() -> VersionInfo {
-    macro_rules! env_str {
-        ($name:expr) => { env!($name).to_string() }
-    }
     macro_rules! option_env_str {
         ($name:expr) => { option_env!($name).map(|s| s.to_string()) }
     }
+
+    // So this is pretty horrible...
+    // There are two versions at play here:
+    //   - version of cargo-the-binary, which you see when you type `cargo --version`
+    //   - version of cargo-the-library, which you download from crates.io for use
+    //     in your projects.
+    //
+    // We want to make the `binary` version the same as the corresponding Rust/rustc release.
+    // At the same time, we want to keep the library version at `0.x`, because Cargo as
+    // a library is (and probably will always be) unstable.
+    //
+    // Historically, Cargo used the same version number for both the binary and the library.
+    // Specifically, rustc 1.x.z was paired with cargo 0.x+1.w.
+    // We continue to use this scheme for the library, but transform it to 1.x.w for the purposes
+    // of `cargo --version`.
+    let major = 1;
+    let minor = env!("CARGO_PKG_VERSION_MINOR").parse::<u8>().unwrap() - 1;
+    let patch = env!("CARGO_PKG_VERSION_PATCH").parse::<u8>().unwrap();
+
     match option_env!("CFG_RELEASE_CHANNEL") {
         // We have environment variables set up from configure/make.
         Some(_) => {
@@ -210,9 +226,9 @@ pub fn version() -> VersionInfo {
                     }
                 });
             VersionInfo {
-                major: env_str!("CARGO_PKG_VERSION_MAJOR"),
-                minor: env_str!("CARGO_PKG_VERSION_MINOR"),
-                patch: env_str!("CARGO_PKG_VERSION_PATCH"),
+                major,
+                minor,
+                patch,
                 pre_release: option_env_str!("CARGO_PKG_VERSION_PRE"),
                 cfg_info: Some(CfgInfo {
                     release_channel: option_env_str!("CFG_RELEASE_CHANNEL").unwrap(),
@@ -223,9 +239,9 @@ pub fn version() -> VersionInfo {
         // We are being compiled by Cargo itself.
         None => {
             VersionInfo {
-                major: env_str!("CARGO_PKG_VERSION_MAJOR"),
-                minor: env_str!("CARGO_PKG_VERSION_MINOR"),
-                patch: env_str!("CARGO_PKG_VERSION_PATCH"),
+                major,
+                minor,
+                patch,
                 pre_release: option_env_str!("CARGO_PKG_VERSION_PRE"),
                 cfg_info: None,
             }