Simplify formatter check (JuliaIO#1078)

This will display the diff, and return a non-zero exit code if there are changes

.github/workflows/Format-check.yml

@@ -28,12 +28,4 @@ jobs:
           julia -e 'using JuliaFormatter; format(["src", "test", "deps", "filters", "gen"], verbose=true)'
       - name: Format check
         run: |
-          julia -e '
-          out = Cmd(`git diff --name-only`) |> read |> String
-          if out == ""
-              exit(0)
-          else
-              @error "Some files have not been formatted !!!"
-              write(stdout, out)
-              exit(1)
-          end'
+          git diff --color=always --exit-code