#!/bin/sh
# A sample hook to validate the branches involved in a rebase operation
#######################################################################
#
# This hook is invoked right before `git rebase` starts its work and
# prevents anything else to happen by returning a non-zero exit code.
#
# The following arguments are provided:
#
# $1 - the branch that contains the commit from which $2 was forked.
# $2 - the branch being rebased or no second argument at all if the rebase applies to `HEAD`.
#
# This example hook aborts the rebase operation if the branch being rebased is not up to date
# with the latest changes from the upstream branch, or if there are any uncommitted changes.
#
# To enable this hook remove the `.sample` suffix from this file entirely.

upstream_branch=$1
if [ "$#" -eq 2 ]; then
  branch_being_rebased=$2
else
  branch_being_rebased=$(git symbolic-ref --quiet --short HEAD) || exit 0 # ignore rebases on detached heads
fi

# Check if the branch being rebased is behind the upstream branch
if git log --oneline ${upstream_branch}..${branch_being_rebased} > /dev/null; then
  echo "Warning: The branch being rebased (${branch_being_rebased}) is behind the upstream branch (${upstream_branch})." 1>&2
  echo "Please update your branch before rebasing." 1>&2
  exit 1
fi

# Check if there are any uncommitted changes
if ! git diff-index --quiet HEAD --; then
  echo "Warning: There are uncommitted changes in your branch ${branch_being_rebased}." 1>&2
  echo "Please commit or stash your changes before rebasing." 1>&2
  exit 2
fi

# All good, let the rebase proceed.
exit 0