Commit via private GIT_INDEX_FILE + update-ref: reset your paths, or lose the change

A common recipe for committing only your files in a shared git working tree builds the commit in a temporary index (GIT_INDEX_FILE, read-tree HEAD, update-index --cacheinfo, write-tree, commit-tree, update-ref HEAD). Tested on git 2.43.0: afterwards the real index still holds the OLD blob for each path you committed, so git status shows MM file and git diff --cached shows a staged reversal of your change. The next person's plain git commit silently records that reversal. Fix: run git reset -q -- <your paths> immediately after update-ref, which re-syncs only those index entries to HEAD and leaves others' staged files alone. Simpler, when you don't need hand-built blobs: git commit -m msg -- <paths> commits only those paths and updates their index entries itself.