component: Support installation/removal of component-target

In order to reduce the surprise available when someone expects to be able to
take output of `rustup component list` and use it as input to `rustup component
add` or `rustup component remove` we now support creation of `Component`
objects by attempting to split it on '-' and see if we get a component name and
valid full target triple.

Fixes: #2057

src/cli/rustup_mode.rs

@@ -1127,7 +1127,8 @@ fn component_add(cfg: &Cfg, m: &ArgMatches<'_>) -> Result<()> {
     });
 
     for component in m.values_of("component").expect("") {
-        let new_component = Component::new(component.to_string(), target.clone(), true);
+        let new_component = Component::new_with_target(component, false)
+            .unwrap_or_else(|| Component::new(component.to_string(), target.clone(), true));
 
         toolchain.add_component(new_component)?;
     }
@@ -1146,7 +1147,8 @@ fn component_remove(cfg: &Cfg, m: &ArgMatches<'_>) -> Result<()> {
     });
 
     for component in m.values_of("component").expect("") {
-        let new_component = Component::new(component.to_string(), target.clone(), true);
+        let new_component = Component::new_with_target(component, false)
+            .unwrap_or_else(|| Component::new(component.to_string(), target.clone(), true));
 
         toolchain.remove_component(new_component)?;
     }

src/dist/manifest.rs

@@ -13,7 +13,7 @@
 use crate::errors::*;
 use crate::utils::toml_utils::*;
 
-use crate::dist::dist::{Profile, TargetTriple};
+use crate::dist::dist::{PartialTargetTriple, Profile, TargetTriple};
 use std::collections::HashMap;
 use std::hash::{Hash, Hasher};
 use std::str::FromStr;
@@ -496,6 +496,24 @@ impl Component {
             is_extension,
         }
     }
+
+    pub fn new_with_target(pkg_with_target: &str, is_extension: bool) -> Option<Self> {
+        for (pos, _) in pkg_with_target.match_indices('-') {
+            let pkg = &pkg_with_target[0..pos];
+            let target = &pkg_with_target[pos + 1..];
+            if let Some(partial) = PartialTargetTriple::new(target) {
+                if partial.arch.is_some() && partial.os.is_some() && partial.env.is_some() {
+                    return Some(Self {
+                        pkg: pkg.to_string(),
+                        target: Some(TargetTriple::new(target)),
+                        is_extension,
+                    });
+                }
+            }
+        }
+        None
+    }
+
     pub fn wildcard(&self) -> Self {
         Self {
             pkg: self.pkg.clone(),