Delete suggestions of removing the relevant component from component_unavailable_msg

After digging into the codebase, I realized that the message generated
by `component_unavailable_msg` is used only when:

- Some components are missing from the toolchain so that the
  installation can no longer proceed;
- We are not installing these components as a part of a
  toolchain-wide operation (e.g. updating the existing `nightly`),
  which is covered by `components_missing_msg` by catching the
  `RustupError::RequestedComponentsUnavailable` and re-throwing
  it as a `DistError::ToolchainComponentsMissing`
  (see <#3453 (comment)>
  for more info).

Thus, I decided to remove the `rustup component remove` suggestion
altogether.

Author: rami3l

src/errors.rs

@@ -19,14 +19,6 @@ use crate::{
     toolchain::names::{PathBasedToolchainName, ToolchainName},
 };
 
-const TOOLSTATE_MSG: &str =
-    "If you require these components, please install and use the latest successful build version,\n\
-     which you can find at <https://rust-lang.github.io/rustup-components-history>.\n\nAfter determining \
-     the correct date, install it with a command such as:\n\n    \
-     rustup toolchain install nightly-2018-12-27\n\n\
-     Then you can use the toolchain with commands such as:\n\n    \
-     cargo +nightly-2018-12-27 build";
-
 /// A type erasing thunk for the retry crate to permit use with anyhow. See <https://github.com/dtolnay/anyhow/issues/149>
 #[derive(Debug, ThisError)]
 #[error(transparent)]
@@ -147,29 +139,6 @@ fn suggest_message(suggestion: &Option<String>) -> String {
     }
 }
 
-fn remove_component_msg(cs: &Component, manifest: &Manifest, toolchain: &str) -> String {
-    if cs.short_name_in_manifest() == "rust-std" {
-        // We special-case rust-std as it's the stdlib so really you want to do
-        // rustup target remove
-        format!(
-            "    rustup target remove --toolchain {} {}",
-            toolchain,
-            cs.target.as_deref().unwrap_or(toolchain)
-        )
-    } else {
-        format!(
-            "    rustup component remove --toolchain {}{} {}",
-            toolchain,
-            if let Some(target) = cs.target.as_ref() {
-                format!(" --target {target}")
-            } else {
-                String::default()
-            },
-            cs.short_name(manifest)
-        )
-    }
-}
-
 /// Returns a error message indicating that certain [`Component`]s are unavailable.
 ///
 /// # Panics
@@ -179,24 +148,19 @@ fn component_unavailable_msg(cs: &[Component], manifest: &Manifest, toolchain: &
     match cs {
         [] => panic!("`component_unavailable_msg` should not be called with an empty collection of unavailable components"),
         [c] => {
-             _ = writeln!(
+            _ = writeln!(
                 buf,
                 "component {} is unavailable for download for channel '{}'",
                 c.description(manifest),
                 toolchain,
             );
+
             if toolchain.starts_with("nightly") {
-                 _ = write!(
+                _ = write!(
                     buf,
                     "Sometimes not all components are available in any given nightly. "
                 );
             }
-             _ = write!(
-                buf,
-                "If you are trying to update an existing toolchain and no longer need this component,\n\
-                you might want to remove it first with:\n\n{}\n\n{TOOLSTATE_MSG}",
-                remove_component_msg(c, manifest, toolchain)
-            );
         }
         cs => {
             // More than one component
@@ -216,27 +180,17 @@ fn component_unavailable_msg(cs: &[Component], manifest: &Manifest, toolchain: &
                     .join(", ")
             };
 
-            let remove_msg = cs
-                .iter()
-                .map(|c| remove_component_msg(c, manifest, toolchain))
-                .collect::<Vec<_>>()
-                .join("\n");
-
             _ = write!(
                 buf,
                 "some components unavailable for download for channel '{toolchain}': {cs_str}"
             );
+
             if toolchain.starts_with("nightly") {
                 _ = write!(
                     buf,
                     "Sometimes not all components are available in any given nightly. "
                 );
             }
-            _ = write!(
-                    buf,
-                    "If you are trying to update an existing toolchain and no longer need these components,\n\
-                    you might want to remove them first with:\n\n{remove_msg}\n\n{TOOLSTATE_MSG}",
-            );
         }
     }