histedit.rb

require "json"
require "set"
require "tempfile"

def get_chain
  output = `jj log -r 'trunk()..@' --no-graph -T '"[" ++ json(description.first_line()) ++ "," ++ json(change_id) ++ "]\n"'`
  if $? != 0
    raise "jj failed"
  end
  output.each_line.map do |line|
    desc, change = JSON.parse(line)
    [desc, change]
  end.to_a
end

def formatted(chain)
  lines = chain.map do |item|
    desc, change = item
    if desc.empty?
      desc = 'no description'
    end
    "#{change} # #{desc}"
  end.join("\n")
  "JJ: newest\n#{lines}\nJJ: oldest"
end

def parse_order(contents, previous)
  ids = Set.new(previous)
  changes = []
  contents.each_line do |line|
    m = line.match(/^(\w+) #/)
    unless m
      puts "invalid line: #{line}"
      next
    end
    id = m[1]
    unless ids.include? id
      puts "wrong id: #{id}"
      next
    end
    changes << id
  end
  changes
end

def histedit(old_order, new_order)
  system 'jj', 'parallelize', old_order.join('|')
  prev = 'trunk()'
  new_order.reverse_each do |change|
    system 'jj', 'rebase', '-s', change, '-o', prev
    prev = change
  end
end

chain = get_chain
change_order = chain.map { |c| c[1] }

Tempfile.create ['jj-histedit-', '.jjdescription'] do |file|
  fmt = formatted(chain)
  File.write(file, fmt)

  system 'vim', file.path

  altered = File.read(file.path)
  if altered == fmt
    puts "no changes"
    exit 0
  end
  new_order = parse_order(altered, change_order)
  histedit(change_order, new_order)
end