Include prettyplease version in --version

Cargo.lock

@@ -515,9 +515,9 @@ dependencies = [
 
 [[package]]
 name = "prettyplease"
-version = "0.1.11"
+version = "0.1.12"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "f28f53e8b192565862cf99343194579a022eb9c7dd3a8d03134734803c7b3125"
+checksum = "e5355b9d4fc0cc607db0c2e93c7a035a32226bfa770e0c6fec504f0018015bad"
 dependencies = [
  "proc-macro2",
  "syn",

Cargo.toml

@@ -16,7 +16,7 @@ autotests = false
 atty = "0.2"
 cargo-subcommand-metadata = "0.1"
 clap = { version = "3.2.5", default-features = false, features = ["deprecated", "derive", "std", "suggestions"] }
-prettyplease = { version = "0.1", optional = true }
+prettyplease = { version = "0.1.12", optional = true }
 proc-macro2 = "1.0"
 quote = { version = "1.0", default-features = false }
 serde = { version = "1.0", features = ["derive"] }

build.rs

@@ -0,0 +1,18 @@
+use std::env;
+use std::fs;
+use std::path::PathBuf;
+
+fn main() {
+    let mut version = env!("CARGO_PKG_VERSION").to_owned();
+    if cfg!(feature = "prettyplease") {
+        if let Ok(prettyplease_version) = env::var("DEP_PRETTYPLEASE01_VERSION") {
+            // TODO: Make this appear only if `--version --verbose` is used.
+            version.push_str(" + prettyplease ");
+            version.push_str(&prettyplease_version);
+        }
+    }
+
+    let out_dir = PathBuf::from(env::var("OUT_DIR").unwrap());
+    let version_file = out_dir.join("version");
+    fs::write(version_file, version).unwrap();
+}

src/opts.rs

@@ -4,13 +4,15 @@ use std::path::PathBuf;
 use std::str::FromStr;
 use syn_select::Selector;
 
+const VERSION: &str = include_str!(concat!(env!("OUT_DIR"), "/version"));
+
 #[derive(Parser)]
-#[clap(bin_name = "cargo", version, author)]
+#[clap(bin_name = "cargo", version = VERSION, author)]
 pub enum Opts {
     /// Show the result of macro expansion.
     #[clap(
         name = "expand",
-        version,
+        version = VERSION,
         author,
         setting = AppSettings::DeriveDisplayOrder,
         dont_collapse_args_in_usage = true