feat: Add custom completer for cargo <TAB> to complete aliases defined in config.toml

Author: nooma-42

src/bin/cargo/cli.rs

@@ -571,6 +571,8 @@ pub fn cli(gctx: &GlobalContext) -> Command {
             .invalid(style::INVALID)
     };
 
+    let alias_map = super::user_defined_aliases(gctx);
+
     Command::new("cargo")
         // Subcommands all count their args' display order independently (from 0),
         // which makes their args interspersed with global args. This puts global args last.
@@ -691,6 +693,20 @@ See '<cyan,bold>cargo help</> <cyan><<command>></>' for more information on a sp
                 }))
             }).collect()
         })))
+        .add(clap_complete::engine::SubcommandCandidates::new(move || {
+            alias_map.iter()
+                .map(|(alias, cmd_info)| {
+                    let help_text = if let super::CommandInfo::Alias { target } = cmd_info {
+                        let cmd_str = target.iter().map(String::as_str).collect::<Vec<_>>().join(" ");
+                        format!("alias for {}", cmd_str)
+                    } else {
+                        "alias (from config)".to_string()
+                    };
+                    clap_complete::CompletionCandidate::new(alias.clone())
+                        .help(Some(help_text.into()))
+                })
+                .collect()
+        }))
         .subcommands(commands::builtin())
 }