Post checkout hook for managing rails migrations and bundle install

post_checkout_migrations.sh

CHECKING_OUT_BRANCH=$3
OLD_BRANCH=$1
NEW_BRANCH=$2

if [ $CHECKING_OUT_BRANCH -eq 1 ]
  then
    FILES_CHANGED=`git diff $OLD_BRANCH $NEW_BRANCH --name-status`
    MIGRATIONS_REMOVED=`echo "$FILES_CHANGED" | egrep 'D\tdb/migrate/([0-9]+)' | sort -r`
    MIGRATIONS_ADDED=`echo "$FILES_CHANGED" | egrep 'A\tdb/migrate/([0-9]+)'`
    
    # CHECK IF WE NEED TO DO A BUNDLE
    BUNDLE_CHANGED=`echo "$FILES_CHANGED" | egrep 'M\tGemfile.lock'` 
    if [ ! -z "$BUNDLE_CHANGED" ]; then
      echo "Your Gemfile.lock has changed, running bundle"
      bundle
    fi

    if [ ! -z "$MIGRATIONS_REMOVED" ]; then
      echo "Rolling back missing migrations"
      for migration in $MIGRATIONS_REMOVED
      do
        if [ $migration == "D" ]; then
          continue
        fi
        git checkout "$OLD_BRANCH" -- "$migration"
        VERSION=`echo "$migration" | cut -d'_' -f1 | cut -d'/' -f3`
        bundle exec rake db:migrate:down VERSION="$VERSION"
        git reset
        rm "$migration"
      done
      bundle exec rake db:test:prepare
      git checkout db/schema.rb
    fi

    if [ ! -z "$MIGRATIONS_ADDED" ]; then
      echo "New migrations have been added running migrations"
      bundle exec rake db:migrate db:test:prepare
    fi
fi

This grew out of a gist, it now lives at brysgo/git-rails

Small note for readers:

After copying to .git/hooks/post-checkout, run
chmod u+x .git/hooks/post-checkout
to make it executable