When I stage a file, "git status" then mentions that, to UNstage that file, I can do "git reset HEAD filename". But I have also seen instances in which the recommended command is "git reset -- filename".
Sorry, I do not remember the superficial differences between when I have seen "--" recommended instead of "HEAD" but I just now ran a test, in which I attempted to UNstage a file 2 separate times: once using "HEAD" and once using "--", and I cannot see the difference in the results.
(Unless it's absolutely necessary, in order to give me a truly accurate answer, I'm not interested in subtleties about the differences between "HEAD~" and "HEAD~1"; etc; etc. --because I seem to rarely-or-never see those subtleties mentioned in the automatic recommendations that pop up.)
Thanks.