pre_plan_checkout.sh

#!/bin/bash

# Find the commit hash of the last user commit before any Atlantis merge commits.
# Adjust "atlantis-merge" if Atlantis uses a different commit message.
atlantis_commit_pattern="atlantis-merge"

# Get the hash of the first Atlantis merge commit looking backwards from HEAD.
# The "^!" ensures we only get commits with messages not matching the Atlantis pattern.
atlantis_commit=$(git log --pretty=format:'%H %s' | grep -m 1 -B 1 "$atlantis_commit_pattern" | head -n1 | cut -d' ' -f1)

if [ ! -z "$atlantis_commit" ]; then
  # Find the immediate parent commit of the found Atlantis commit, which should be the last user commit.
  user_commit=$(git rev-parse "${atlantis_commit}^")

  if [ ! -z "$user_commit" ]; then
    echo "Checking out to user's last commit $user_commit before Atlantis merge."
    git checkout $user_commit
  else
    echo "Could not find the user's last commit before the Atlantis merge."
  fi
else
  echo "No Atlantis merge commit found. Staying on current commit."
fi