Script to prune any tags which exist locally but not on the remote

git-prune-tags.rb

#!/usr/bin/env ruby

require 'readline'
def prompt(prompt="> ")
  input = nil
  prompt += " " unless prompt =~ /\s$/
  loop do
    input = Readline.readline(prompt)
    break if input.length > 0
  end
  return input
end  

remote  = ARGV[0]
dry_run = ARGV.include?("--dry-run")

if !remote || remote == "--dry-run"
  puts "no remote specified, assuming 'origin'"
  remote = "origin"
end

local_tags  = `git tag`.split("\n")
remote_tags = []

remote_tag_details = `git ls-remote --tags #{remote}`.split("\n")
remote_tag_details.each do |details|
  sha, tag = details.split("\t")  
  next if tag[-3, 3] == "^{}"
  remote_tags << tag.gsub(%r(^refs/tags/), '')
end

delete_tags = []
local_tags.each do |local_tag|
  next if remote_tags.include?(local_tag)
  puts "local tag '#{local_tag}' not found in '#{remote}'"
  delete_tags << local_tag
end

if delete_tags.empty?
  abort "No tags found locally which aren't on '#{remote}'"
end

if dry_run
  puts "#{delete_tags.size} tags would have been deleted, run without --dry-run to do the deed"
else
  response = prompt("Are you sure you want to delete these tags? (yn)")
  if response.downcase.strip =~ /^y/
    delete_tags.each do |local_tag|
      `git tag -d #{local_tag}`  
    end

    puts "#{delete_tags.size} tags have been deleted"  
  else
    puts "Aborted"
  end    
end

What is the license for this code?

If not copyrighted would you mind adding:
/*
Not copyrighted -- provided to the public domain
*/

Just do:

git tag -l | xargs git tag -d
git fetch

Won't that delete every local tag?

@julias-shaw yes it will
Isn't this the idea of pruning is to remove local tags that no longer exist on the remote?
This will make it so you're up to date with the remote 1:1.
If you want to keep your local clean though this is not for you.

there was an update making this obsolete ;)

git fetch --prune --prune-tags