Updated Directive (markdown)

Directive.md

@@ -10,11 +10,27 @@ Supported directives are `disable` to disable warnings:
     # shellcheck disable=code[,code...]
     statement_where_warning_should_be_disabled
 
-and `source` to tell ShellCheck where to find a sourced file:
+`source` to tell ShellCheck where to find a sourced file:
 
     # shellcheck source=src/examples/config.sh
     . "$(locate_config)"
 
-Directives are scoped to the structure that follows it. For example, before a function it silences all warnings (or overrides all `source` statements) in the function Before a case statement, it silences all warnings in all branches of the case statement.
+`shell`, as a top level directive, to specify the shell for a script (like the shebang, if you for any reason don't want to add one):
+
+    # shellcheck shell=sh
+    echo foo &> bar
+
+Directives instead of or immediately after the shebang apply to the entire script. Otherwise, they are scoped to the structure that follows it (such as all branches of a `case` statement`, or an entire function).
+
+There is no support for scoping a directive to the first structure of the script. In these cases, use a dummy command `true` or `:` and then add directives, such as
+
+    # This directive applies to the entire script
+    # shellcheck disable=2086
+    true
+    # This directive only applies to this function
+    # shellcheck disable=2043
+    f() {
+      ...
+    }
 
 Silencing parser errors is purely cosmetic, and will not make ShellCheck continue.