Clarify --version usage and add a warning at runtime (#116)

Fixes #113

Cargo.lock

@@ -1186,9 +1186,9 @@ dependencies = [
 
 [[package]]
 name = "regex"
-version = "1.5.4"
+version = "1.5.5"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "d07a8629359eb56f1e2fb1652bb04212c072a87ba68546a04065d525673ac461"
+checksum = "1a11647b6b25ff05a515cb92c365cec08801e83423a235b51e231e1808747286"
 dependencies = [
  "aho-corasick",
  "memchr",
@@ -1356,9 +1356,9 @@ dependencies = [
 
 [[package]]
 name = "semver"
-version = "1.0.5"
+version = "1.0.7"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "0486718e92ec9a68fbed73bb5ef687d71103b142595b406835649bebd33f72c7"
+checksum = "d65bd28f48be7196d222d95b9243287f48d27aca604e08497513019ff0502cc4"
 dependencies = [
  "serde",
 ]

Cargo.toml

@@ -37,7 +37,7 @@ strum_macros = "0.23.1"
 strum = "0.23.0"
 dirs = "4.0.0"
 crates-index = "0.18.5"
-semver = "1.0.5"
+semver = "1.0.7"
 xz2 = "0.1.6"
 zip = "0.5.13"
 async-trait = "0.1.52"

src/main.rs

@@ -1,4 +1,4 @@
-use std::path::PathBuf;
+use std::{path::PathBuf, str::FromStr};
 
 use log::{debug, error, info, warn, LevelFilter};
 use simplelog::{ColorChoice, ConfigBuilder, TermLogger, TerminalMode};
@@ -20,7 +20,8 @@ struct Options {
     #[structopt()]
     name: String,
 
-    /// Filter for package version to install
+    /// Filter for package version to install, in Cargo.toml format.
+    /// Use `=1.2.3` to install a specific version.
     #[structopt(long, default_value = "*")]
     version: String,
 
@@ -104,6 +105,19 @@ async fn main() -> Result<(), anyhow::Error> {
     let manifest = load_manifest_path(manifest_path.join("Cargo.toml"))?;
     let package = manifest.package.unwrap();
 
+    let is_plain_version = semver::Version::from_str(&opts.version).is_ok();
+    if is_plain_version && package.version != opts.version {
+        warn!(
+            "You specified `--version {o}` but the package resolved that to '{p}', use `={o}` if you want an exact match",
+            o=opts.version, p=package.version
+        );
+
+        if !opts.no_confirm && !opts.dry_run && !confirm()? {
+            warn!("Installation cancelled");
+            return Ok(());
+        }
+    }
+
     let (mut meta, binaries) = (
         package
             .metadata