#!/usr/bin/env bash
#
# mfup
#
# - Fetch latest upstream and replace the PR Target branch with 
# - Rebase the (current or specified) branch on the PR Target
# - Force-push the branch to 'origin'
# - 
#

[[ $# < 2 ]] || { echo "Usage: `basename $0` [branch]" 1>&2 ; exit 1; }

MFINFO=$(mfinfo "$@") || exit 1
IFS=' ' read -a INFO <<< "$MFINFO"
ORG=${INFO[0]}
FORK=${INFO[1]}
REPO=${INFO[2]}
TARG=${INFO[3]}
BRANCH=${INFO[4]}
OLDBRANCH=${INFO[5]}

set -e

# Prevent accidental loss of current changes
[[ $(git stash) != "No local "* ]] && HAS_STASH=1

echo "Fetching upstream ($ORG/$REPO)..."
git fetch upstream

echo ; echo "Bringing $TARG up to date..."
if [[ git checkout -q $TARG ]]; then
  git reset --hard upstream/$TARG
  git push -f origin
else
  git checkout upstream/$TARG -b $TARG
  git push --set-upstream origin $TARG
fi

if [[ $BRANCH != $TARG ]]; then
  echo ; echo "Rebasing $BRANCH on $TARG..."
  if git checkout $BRANCH; then
    echo
    if git rebase $TARG; then
      git push -f
    else
      echo "Looks like merge conflicts. Stopping here." ; exit
    fi
  else
    echo "No such branch!"
  fi
fi

echo
[[ $BRANCH != $OLDBRANCH ]] && git checkout $OLDBRANCH

[[ $HAS_STASH == 1 ]] && git stash pop