In https://gerrit.wikimedia.org/r/c/mediawiki/libs/Equivset/+/604545 only a few lines have been added to the data/equivset.in file, but Gerrit shows every line of the file in its diff view (link).
I ran a git diff HEAD~1 on the change, and it looks like newline characters (^M as terminal calls them, \r in programming parlance) were added to the end of the lines, but I cannot find such character in the file itself. Even if they were added, the diff view of Gerrit is not being super helpful because it should at least show a red box (like it does for extra spaces or extra \n characters).
Set diff preference Ignore Whitespace to All to reduce the difference. Or locally use git show -w to ignore whitespaces.