setMainIs :: FilePath -> String -> Sh ()
setMainIs cabalPath mainFile = sed cabalPath $ \line ->
    if "-- main-is:" `T.isInfixOf` line
        then takeWhile C.isSpace line <> "main-is:             " <> T.pack mainFile
        else line
setMainIs :: FilePath -> String -> Sh ()
setMainIs cabalPath mainFile = sed cabalPath $ \line ->
    if "-- main-is:" `T.isInfixOf` line
        then takeWhile C.isSpace line <> "main-is:             " <> T.pack mainFile
        else line
setMainIs cabalPath mainFile = sed cabalPath $ \line ->
    if "-- main-is:" `T.isInfixOf` line
        then takeWhile C.isSpace line <> "main-is:             " <> T.pack mainFile
        else line