git-prune-merged-branches

#!/usr/bin/env ruby

force = ARGV.include? "-f"

current_branch = `git symbolic-ref --short HEAD`.chomp

remote_branches = `git branch -r --list`.
  split("\n").
  map(&:strip).
  map{|a|a.split("/")[1..-1].join("/")}

local_branches = `git branch --list --merged`.
  gsub(/^\* /, '').
  split("\n").
  map(&:strip)

merged_branches = local_branches - remote_branches - [current_branch]

if merged_branches.empty?
  puts "No existing local branches have been merged into #{current_branch}."
else
  puts "Local branches merged into #{current_branch} found:"
  puts merged_branches.join("\n")
  puts "Remove branches? (y/N)"
  if force || gets =~ /^y/i
    # Remove local branches
    `git branch -d #{merged_branches.join(' ')}`
  end
end