커밋을 임시 인덱스에서 빚어

# Everything below runs against a THROWAWAY index file. The
# repository's own index - which a neighbor session may have 92
# files staged in - is neither read nor written.

export GIT_INDEX_FILE="$(mktemp -u)"

# the CAS's expected old value: where the branch is RIGHT NOW.
# Not the base - see step 5.
LOCAL=$(git rev-parse refs/heads/main)

# 1. start from the base we deliberately chose (next lesson)
git read-tree "$BASE"

# 2. add exactly our paths, from the working tree
git add -- content/target/            # OUR material only; the shared
                                      # wiring is a separate pass (L05)

# 3. write a tree object and a commit object. NO HOOKS FIRE.
TREE=$(git write-tree)
NEW=$(git commit-tree "$TREE" -p "$BASE" -m "$MESSAGE")

# 4. leak check BEFORE moving anything: the commit must touch
#    nothing outside the paths this operation is allowed to.
git diff-tree --no-commit-id --name-only -r "$NEW" \
  | grep -qvE '^content/target/' \
  && { echo "refusing: commit touches paths outside land_paths"; exit 1; }

# 5. move the branch by COMPARE-AND-SWAP. The expected old value is
#    the branch's CURRENT tip, NOT the base we built on. When the
#    base came from the remote the two differ, and a swap against
#    the base would reject every time - in precisely the behind
#    case this is for. Fails cleanly if somebody moved it while we
#    were working; rebuild, never force.
git update-ref refs/heads/main "$NEW" "$LOCAL"

# The ordinary human `git commit` in this same checkout still runs
# its hooks and still does the work they do. Only the automated
# landing - which gained nothing from them - routes around.