git-revert-merges

#!/bin/bash

# Revert merges between two commits

if [ $# -eq 0 ]; then
echo "Usage: $0 start target"
echo ""
echo "start = SHA of starting commit (or HEAD, etc.)"
echo "target = SHA of target commit"
echo ""
echo "Reverts all merge commits from HEAD to the target commit. Use at your own risk."
echo ""
exit 1
fi

start=$1
target=$2

# Exit on any error so we don't screw anything up
set -e

echo "Reverting from ${start} to ${target}..."
echo ""
sleep 1

# Build the list of commits to revert
commits=$(git rev-list ${target}..${start})
merges=()

for sha in ${commits}; do
  # Look for merge commits; check if they are merges before attempting to revert
  if [[ $(git cat-file -p ${sha} | grep '^parent ' | wc -l) -ge 2 ]]; then
    # This commit has two parents, it is a merge
    merges+=( "${sha}" )
  fi
done

echo "These merge commits will be reverted:"
for line in ${merges[@]}; do
  echo "${line}"
done
echo ""
sleep 2

for sha in ${merges[@]}; do
  # Revert each commit; use the 1st parent (the branch merged into) as the mainline
  echo "Reverting: ${sha}"
  git revert -m 1 --no-commit ${sha}
  echo "Reverted."
done

echo "Reverts are complete."