fix(multicall): Improve bad multicall binary error

By removing all arguments, we've switched from an "unrecognized
argument" error to a "unrecognized subcommand" error.  While the wording
has room for improvement, its at least progress on #2862.

examples/repl.rs

@@ -66,7 +66,6 @@ fn cli() -> Command<'static> {
     Command::new("repl")
         .multicall(true)
         .arg_required_else_help(true)
-        .disable_help_flag(true)
         .subcommand_required(true)
         .subcommand_value_name("APPLET")
         .subcommand_help_heading("APPLETS")

src/build/command.rs

@@ -4025,6 +4025,14 @@ impl<'help> App<'help> {
             // Make sure all the globally set flags apply to us as well
             self.settings = self.settings | self.g_settings;
 
+            #[cfg(feature = "unstable-multicall")]
+            {
+                if self.is_set(AppSettings::Multicall) {
+                    self.settings.insert(AppSettings::DisableHelpFlag.into());
+                    self.settings.insert(AppSettings::DisableVersionFlag.into());
+                }
+            }
+
             self._propagate();
             self._check_help_and_version();
             self._propagate_global_args();

tests/builder/subcommands.rs

@@ -517,7 +517,7 @@ fn busybox_like_multicall() {
 
     let m = cmd.clone().try_get_matches_from(&["a.out"]);
     assert!(m.is_err());
-    assert_eq!(m.unwrap_err().kind(), ErrorKind::UnknownArgument);
+    assert_eq!(m.unwrap_err().kind(), ErrorKind::UnrecognizedSubcommand);
 }
 
 #[cfg(feature = "unstable-multicall")]
@@ -539,7 +539,7 @@ fn hostname_like_multicall() {
 
     let m = cmd.clone().try_get_matches_from(&["a.out"]);
     assert!(m.is_err());
-    assert_eq!(m.unwrap_err().kind(), ErrorKind::UnknownArgument);
+    assert_eq!(m.unwrap_err().kind(), ErrorKind::UnrecognizedSubcommand);
 
     let m = cmd.try_get_matches_from_mut(&["hostname", "hostname"]);
     assert!(m.is_err());
@@ -549,3 +549,56 @@ fn hostname_like_multicall() {
     assert!(m.is_err());
     assert_eq!(m.unwrap_err().kind(), ErrorKind::UnknownArgument);
 }
+
+#[cfg(feature = "unstable-multicall")]
+#[test]
+fn bad_multicall_command_error() {
+    let cmd = Command::new("repl")
+        .version("1.0.0")
+        .propagate_version(true)
+        .multicall(true)
+        .subcommand(Command::new("foo"))
+        .subcommand(Command::new("bar"));
+
+    let err = cmd.clone().try_get_matches_from(&["world"]).unwrap_err();
+    assert_eq!(err.kind(), ErrorKind::UnrecognizedSubcommand);
+    static HELLO_EXPECTED: &str = "\
+error: The subcommand 'world' wasn't recognized
+
+USAGE:
+     <subcommands>
+
+For more information try help
+";
+    utils::assert_eq(HELLO_EXPECTED, err.to_string());
+
+    let err = cmd.clone().try_get_matches_from(&["baz"]).unwrap_err();
+    assert_eq!(err.kind(), ErrorKind::InvalidSubcommand);
+    static BAZ_EXPECTED: &str = "\
+error: The subcommand 'baz' wasn't recognized
+
+\tDid you mean 'bar'?
+
+If you believe you received this message in error, try re-running with ' -- baz'
+
+USAGE:
+     [SUBCOMMAND]
+
+For more information try help
+";
+    utils::assert_eq(BAZ_EXPECTED, err.to_string());
+
+    // Verify whatever we did to get the above to work didn't disable `--help` and `--version`.
+
+    let err = cmd
+        .clone()
+        .try_get_matches_from(&["foo", "--help"])
+        .unwrap_err();
+    assert_eq!(err.kind(), ErrorKind::DisplayHelp);
+
+    let err = cmd
+        .clone()
+        .try_get_matches_from(&["foo", "--version"])
+        .unwrap_err();
+    assert_eq!(err.kind(), ErrorKind::DisplayVersion);
+}