chkIsStack :: StackTag ()
chkIsStack = do
  StackTagOpts {optsStackYaml=stackYaml} <- ask
  sYaml <- io $ doesFileExist "stack.yaml"

  case stackYaml of
    Nothing -> unless sYaml $ error "stack.yaml not found or specified!"
    _       -> return ()
chkIsStack :: StackTag ()
chkIsStack = do
  StackTagOpts {optsStackYaml=stackYaml} <- ask
  sYaml <- io $ doesFileExist "stack.yaml"

  case stackYaml of
    Nothing -> unless sYaml $ error "stack.yaml not found or specified!"
    _       -> return ()
chkIsStack = do
  StackTagOpts {optsStackYaml=stackYaml} <- ask
  sYaml <- io $ doesFileExist "stack.yaml"

  case stackYaml of
    Nothing -> unless sYaml $ error "stack.yaml not found or specified!"
    _       -> return ()