Quick command to automatically find the parent branch to stack as a base branch when creating a PR on GitHub

gh_stack

#!/usr/bin/env ruby

current = `git branch --show-current`.strip

branches = `git for-each-ref --format='%(refname:short)' refs/heads/`.split
branches.reject! { |b| b == current }

base = branches
  .map { |b| [b, `git rev-list --count #{b}..#{current}`.strip.to_i] }
  .min_by { |_, count| count }
  &.first

if base
  puts "Base: #{base}"
  exec "gh", "pr", "create", "-B", base, *ARGV
else
  exec "gh", "pr", "create", *ARGV
end

Usage:

$ gh_stack
Base: prev_branch
[gh pr interactive cli]

instead of

$ gh pr create -B prev_branch
[gh pr interactive cli]

This also works if the base branch is master

$ gh_stack
Base: master
[gh pr interactive cli]