Describe the bug
Related #741 , --mode check does not detect no trailing newline and returns Exit code 0.

To Reproduce
example.hs (no trailing newline file)

main = putStrLn "Hello, world!"

command

$ ./ormolu-Linux -v
ormolu 0.1.4.1 HEAD 7714b5220e3c559a764fc9c68fdfb4f6dc439ec7
using ghc-lib-parser 8.10.2.20200916
$ ./ormolu-Linux --mode check example.hs 
$ echo $?
0

Expected behavior

$ ./ormolu-Linux --mode check example.hs
# Message that there's no trailing newline
$ echo $?
100

Environment

• OS name + version: Ubuntu 20.04
• Version of the code: ormolu 0.1.4.1 HEAD 7714b52

Additional context
As amesgen mentioned in #741 , formatting to add trailing newline works fine. Maybe diff detection part does not detect no trailing newline.

Diff detection in --mode check uses diffText function.

This diffText function uses T.lines

T.lines works like below, so difference between "no trailing newline Text" with "formatted Text with trailing newline" is ignored?

$ ghci
GHCi, version 8.6.5: http://www.haskell.org/ghc/  :? for help
Prelude> import qualified Data.Text as T
Prelude T> T.pack "test"
"test"
Prelude T> T.pack "test\n"
"test\n"
Prelude T> T.lines (T.pack "test")
["test"]
Prelude T> T.lines (T.pack "test\n")
["test"]