Add an empty Custom.hs to simplify site-specific patching

src/ShellCheck/Analyzer.hs

@@ -25,6 +25,7 @@ import ShellCheck.Interface
 import Data.List
 import Data.Monoid
 import qualified ShellCheck.Checks.Commands
+import qualified ShellCheck.Checks.Custom
 import qualified ShellCheck.Checks.ShellSupport
 
 
@@ -41,6 +42,7 @@ analyzeScript spec = newAnalysisResult {
 
 checkers params = mconcat $ map ($ params) [
     ShellCheck.Checks.Commands.checker,
+    ShellCheck.Checks.Custom.checker,
     ShellCheck.Checks.ShellSupport.checker
     ]
 

src/ShellCheck/Checks/Custom.hs

@@ -0,0 +1,21 @@
+{-
+    This empty file is provided for ease of patching in site specific checks.
+    However, there are no guarantees regarding compatibility between versions.
+-} 
+
+{-# LANGUAGE TemplateHaskell #-}
+module ShellCheck.Checks.Custom (checker, ShellCheck.Checks.Custom.runTests) where
+
+import ShellCheck.AnalyzerLib
+import Test.QuickCheck
+
+checker :: Parameters -> Checker
+checker params = Checker {
+    perScript = const $ return (),
+    perToken = const $ return ()
+  }
+
+prop_CustomTestsWork = True
+
+return []
+runTests = $quickCheckAll