Make ShellCheck not emit warnings about the shebang if the shell

type is determined from the extension

src/ShellCheck/Analytics.hs

@@ -484,7 +484,7 @@ checkShebang params (T_Annotation _ list t) =
 checkShebang params (T_Script id sb _) = execWriter $ do
     unless (shellTypeSpecified params) $ do
         when (sb == "") $
-            err id 2148 "Tips depend on target shell and yours is unknown. Add a shebang."
+            err id 2148 "Tips depend on target shell and yours is unknown. Add a shebang or an extension to the filename."
         when (executableFromShebang sb == "ash") $
             warn id 2187 "Ash scripts will be checked as Dash. Add '# shellcheck shell=dash' to silence."
     unless (null sb) $ do

src/ShellCheck/AnalyzerLib.hs

@@ -184,7 +184,7 @@ makeParameters spec =
                 Sh   -> False
                 Ksh  -> True,
 
-        shellTypeSpecified = isJust $ asShellType spec,
+        shellTypeSpecified = isJust (asShellType spec) || isJust (asFallbackShell spec),
         parentMap = getParentTree root,
         variableFlow = getVariableFlow params root,
         tokenPositions = asTokenPositions spec