I hope you had not committed to your master locally. If so, this will work:
git checkout master
make update
arc patch D8342
git checkout arcpatch-D8342 # check that the branch name is correct.
# check the log to see commit history.
# make changes you want to make
# git commit with a message
arc diff --update D8342
# after some days
git checkout master
make update
git checkout arcpatch-D8342
git rebase master
# more commits to patch branch, update the diff etc.
Sounds like a pun to me. but it’s most probably the lack of arcanist knowledge.
yay