docs: Clarify args_override_self

Fixes #4357

src/builder/arg.rs

@@ -3521,6 +3521,8 @@ impl Arg {
     ///
     /// **NOTE** [`Arg::exclusive(true)`] allows specifying an argument which conflicts with every other argument.
     ///
+    /// **NOTE:** All arguments implicitly conflict with themselves.
+    ///
     /// # Examples
     ///
     /// ```rust
@@ -3623,8 +3625,6 @@ impl Arg {
     ///
     /// **NOTE:** Overriding an argument implies they [conflict][Arg::conflicts_with`].
     ///
-    /// **NOTE:** All arguments implicitly override themselves.
-    ///
     /// # Examples
     ///
     /// ```rust

src/builder/command.rs

@@ -975,7 +975,10 @@ impl Command {
         }
     }
 
-    /// Specifies that all arguments override themselves.
+    /// Replace prior occurrences of arguments rather than error
+    ///
+    /// For any argument that would conflict with itself by default (e.g.
+    /// [`ArgAction::Set`][ArgAction::Set], it will now override itself.
     ///
     /// This is the equivalent to saying the `foo` arg using [`Arg::overrides_with("foo")`] for all
     /// defined arguments.