#!/bin/sh
# git merge-overlay BRANCHES... - merge all BRANCHES filewise, later branch wins

gitdir=$(git rev-parse --git-dir)
printf no-ff >"$gitdir"/MERGE_MODE
true >"$gitdir"/MERGE_HEAD

msg="Merge overlay branches"
for branch; do
  git checkout --theirs "$branch" -- :/
  printf '%s\n' $branch >>"$gitdir"/MERGE_HEAD
  msg="$msg $branch"
done

printf "%s\n" "$msg" >"$gitdir"/MERGE_MSG
git commit