Checking for merge conflicts without changing working copy

check-merge-conflict.sh

#!/usr/bin/env bash
set -eE

# adapted from http://stackoverflow.com/questions/501407/is-there-a-git-merge-dry-run-option/6283843#6283843

remote_branch=$1

git fetch origin $remote_branch >/dev/null

if git merge-tree `git merge-base FETCH_HEAD HEAD` HEAD FETCH_HEAD | egrep -q '<<<|>>>|changed in both'; then
  echo "No merge conflict"
else
  echo "Branch has merge conflicts with $remote_branch!"
  exit 1
fi

Possibly doesn't detect deletions/moves.