Update git fork with tags and selected branches.

sync_fork.sh

# Repo: apache/flink
# Fork: streamnative/flink

# Prepare the working enviroment

## Clone the forked repository
git clone git@github.com:streamnative/flink.git
## Add the original repository as the upstream git remote
git remote add upstream git@github.com:apache/flink.git

# Main logic

## Fetch the origin and upstream (with tags)
git fetch origin -p
git fetch upstream -p --tags
## Sync master & release-* branch
for branch in $(git ls-remote --heads upstream|sed 's#^.*refs/heads/##'|egrep -i "^(release-|master)"); do
  echo "Sync the branch: ${branch}"
  git push origin refs/remotes/upstream/${branch}:refs/heads/${branch}
done
## Update all the tags
git push --tags
## Update current working branch
git pull