gistfile1.txt

#!/bin/bash
# Usage: gh-rename-master <newbranch> [<remote>]
#
# Renames the "master" branch of the current repository both locally and on GitHub.
# Also attempts to update current user's fork if specified remote is not 'origin'
# 
# Based on https://gist.github.com/mislav/5ac69530acbe1b4ca909e272caabfdba
#
# dependencies: GitHub CLI v0.10
set -e

newbranch="${1?}"
remote="${2:-origin}"

git fetch "$remote" master
git checkout -b "$newbranch" "${remote}/master" --no-track || echo "Branch ${newbranch} already exists locally..."
git push -u "$remote" "$newbranch"
git remote set-head "$remote" "$newbranch"

# update the default branch
echo "Updating default branch for remote..."
gh api -XPATCH "repos/:owner/:repo" -f default_branch="$newbranch" >/dev/null

echo "Updating base branch of outstanding PRs..."
# update the base branch of all open pull requests
for num in $(gh pr list -B master -L999 | cut -f1); do
  gh api -XPATCH "repos/:owner/:repo/pulls/${num}" -f base="$newbranch" >/dev/null
  echo -n .
done

# If specified remote is not "origin", check to see if "origin" is current
# user's fork and if so, update 
if [ "$remote" != "origin" ]; then
  echo "Given remote is not 'origin', checking if 'origin' is personal fork..."

  gh_user=$(gh api user | grep -o '"login":"[^"]*' | cut -d'"' -f4)
  origin_url="$(git config --get remote.origin.url)"

  fork_url_pattern="github\.com[/:]${gh_user}/.*" 

  if [[ $origin_url =~ $fork_url_pattern ]]; then
    echo "Remote 'origin' appears to be personal fork, updating default branch to '${newbranch}'..."

    # `origin` is this users fork, update that too but don't track it
    git push origin "$newbranch"
    git remote set-head origin "$newbranch"

    # update the default branch of our fork
    gh api -XPATCH "repos/${gh_user}/:repo" -f default_branch="$newbranch" >/dev/null
  fi
fi

printf '\nDone!\n'