Pruning remote branches that are already in master

git.rake

namespace :git do

  desc "Remove remote branches that are already merged into master"
  task :prune do
    # never prune these branches, even if they are fully contained in master
    PRESERVE_BRANCHES = %w{production staging master}

    ORIGIN = 'origin'     # remote name
    MASTER = 'master'     # LOCAL branch to compare against

    # Get remote-tracking branches to match origin
    abort unless prompt "Fetch and prune #{ORIGIN}/tracking branches to match #{ORIGIN}?"
    GitHelper.update_tracking_branches(ORIGIN)

    # Ensure on master to do comparison
    abort "Must be on #{MASTER} to find already merged branches." if GitHelper.current_branch != MASTER

    preserve_re = PRESERVE_BRANCHES.join('|')

    # Offer to delete remote branches that are already in (local) master
    branches = GitHelper.merged_branches(:remotes).
               reject { |b| b =~ /(#{preserve_re})$/i || b !~ /^\s*#{ORIGIN}/i }
    if branches.empty?
      puts "No remote branches to prune."
    else
      puts "\nThe following remote branches are fully contained in HEAD of #{GitHelper.current_branch}:"
      puts branches
      abort unless prompt "Delete from #{ORIGIN}? (GitHub)"

      GitHelper.delete!(branches, ORIGIN)
      GitHelper.update_tracking_branches(ORIGIN)
    end

    # Local branches that could be deleted
    branches = GitHelper.merged_branches.reject { |b| b =~ /(#{preserve_re})$/i }
    unless branches.empty?
      puts "\nThe following local branches are fully contained in HEAD of #{GitHelper.current_branch}:"
      puts branches
      puts "\nLocal pruning is left as an exercise for the reader."
    end
  end

  def prompt(question)
    print "\n#{question} [y/N] "
    yes_no = $stdin.gets.chomp
    yes_no.downcase == 'y'
  end

  module GitHelper
    def self.update_tracking_branches(remote='origin')
      # Prune removes remote-tracking branches that no longer exist on the remote
      system("git fetch #{remote} && git remote prune #{remote}")
    end

    # list branches that are already merged into the current branch
    def self.merged_branches(remotes=false)
      out = if remotes
        run_cmd("git branch --remotes --merged") # origin/ tracking branches
      else
        run_cmd("git branch --merged")
      end
      out.split("\n")
    end

    def self.delete!(branches, remote)
      branch_list = branches.map { |b| b.sub(/^\s*#{remote}\//i, '') }.join(' ')  # remove origin/
      system("git push #{remote} --delete #{branch_list}")
    end

    # local branch currently checked out:
    def self.current_branch
      out = run_cmd('git branch')
      $1 if out =~ /\* (\S+)\s/m
    end

    def self.run_cmd(cmd)
      out = `#{cmd}`
      err = $?
      raise "Running `#{cmd}' failed (#{err})." unless err == 0
      out
    end
  end

end

LICENSE

Copyright (C) 2012 Nathan Youngman

Permission is hereby granted, free of charge, to any person obtaining a copy of
this software and associated documentation files (the "Software"), to deal in
the Software without restriction, including without limitation the rights to
use, copy, modify, merge, publish, distribute, sublicense, and/or sell copies
of the Software, and to permit persons to whom the Software is furnished to do
so, subject to the following conditions:

The above copyright notice and this permission notice shall be included in all
copies or substantial portions of the Software.

THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
SOFTWARE.

This isn't really necessary: https://github.com/blog/1335-tidying-up-after-pull-requests