Deletes local branches that have been merged into master

clear_local_branches.rb

branch_prefix = "pt_"
branches_to_keep = []
cmd = `git branch --merged master`
branches = cmd.split("\n").map(&:strip).select{ |b| b.start_with?(branch_prefix) && !branches_to_keep.include?(b) }
branches.each do |branch|
  `git branch -D #{branch}`
end

Without the prefix, maybe?

branches_to_keep = []
cmd = `git branch --merged master`
branches = cmd.split("\n").map(&:strip).select{ |b| !branches_to_keep.include?(b) }
branches.each do |branch|
  `git branch -D #{branch}`
end