Fetch updates from GitHub Pull requests

pr_get

#!/bin/bash -e
# Usage:
# $ pr_get <number>
#
# Configure remote 'upstream': https://help.github.com/en/articles/configuring-a-remote-for-a-fork
# $ git remote add upstream https://github.com/ORIGINAL_OWNER/ORIGINAL_REPOSITORY.git

PR=${1?Missing PR number}
if ! git diff-index --quiet HEAD --; then
  echo "You have uncommited changes. Please commit your changes first"
  exit 1
fi

PR_UPSTREAM=${PR_UPSTREAM:-upstream}

DATE=`date +%m%d`
TARGET_BRANCH=pr${PR}_r

C=0
while true; do
  if [[ $C > 0 ]]; then SUFFIX="_${C}"; else SUFFIX=""; fi
  UPDATE_BRANCH=pr${PR}_${DATE}${SUFFIX}
  if git show-ref --verify --quiet refs/heads/${UPDATE_BRANCH}; then
    C=$((${C}+1))
  else
    break
  fi
done

if git show-ref --verify --quiet refs/heads/${TARGET_BRANCH}; then
  git branch -f ${TARGET_BRANCH}_old ${TARGET_BRANCH}
fi

(
set -x
git fetch ${PR_UPSTREAM} +pull/${PR}/head:${UPDATE_BRANCH}
git checkout -B ${TARGET_BRANCH} FETCH_HEAD
)
echo Done