fix(assert): Provide next steps for '-h' conflicts

For now, we are going to provide a better debug assert in this case.
Resolving clap-rs#3405 is the better long term route.

Fixes clap-rs#3403

src/build/app/mod.rs

@@ -2940,17 +2940,36 @@ impl<'help> App<'help> {
                 self.args.remove(index);
             }
         } else {
-            let other_arg_has_short = self.args.args().any(|x| x.short == Some('h'));
             let help = self
                 .args
-                .args_mut()
+                .args()
                 .find(|x| x.id == Id::help_hash())
                 .expect(INTERNAL_ERROR_MSG);
+            assert_ne!(help.provider, ArgProvider::User);
 
             if help.short.is_some() {
-            } else if !(other_arg_has_short
+                if help.short == Some('h') {
+                    if let Some(other_arg) = self
+                        .args
+                        .args()
+                        .find(|x| x.id != Id::help_hash() && x.short == Some('h'))
+                    {
+                        panic!(
+                            "`help`s `-h` conflicts with `{}`.
+
+To change `help`s short, call `app.arg(Arg::new(\"help\")...)`.",
+                            other_arg.name
+                        );
+                    }
+                }
+            } else if !(self.args.args().any(|x| x.short == Some('h'))
                 || self.subcommands.iter().any(|sc| sc.short_flag == Some('h')))
             {
+                let help = self
+                    .args
+                    .args_mut()
+                    .find(|x| x.id == Id::help_hash())
+                    .expect(INTERNAL_ERROR_MSG);
                 help.short = Some('h');
             } else {
                 debug!("App::_check_help_and_version: Removing `-h` from help");

tests/builder/help.rs

@@ -1557,7 +1557,7 @@ fn arg_short_conflict_with_help() {
 
 #[cfg(debug_assertions)]
 #[test]
-#[should_panic = "Short option names must be unique for each argument, but '-h' is in use by both 'home' and 'help'"]
+#[should_panic = "`help`s `-h` conflicts with `home`."]
 fn arg_short_conflict_with_help_mut_arg() {
     let _ = App::new("conflict")
         .arg(Arg::new("home").short('h'))