You have made same changes in a file (or multiple files) and you want to discard the changes without commiting.
You either want to dicard the changes in a single file or all changes in all the files.

If your intention is to discard changes in a single file then do the following;
git checkout -- <file-name>

If your intention is to discard changes in all files then do the following;
git checkout -- .

You have made