git-merge-from-svn

#!/usr/bin/env ruby

require 'fileutils'

$name = "git merge-from-svn"

def usage retcode=0
  puts <<USAGE
usage: #{$name} [options] <ref>
  -b <name>, --branch_name=<name> select the svn branch name
  -e, --edit                      edit the message before commit
  -l, --log                       show log in message (as in git merge)
  -m <msg>, --message=<msg>       change default message
USAGE
  exit retcode
end

def die msg, usage=false
  $stderr.puts msg
  usage ? usage(-1) : exit(-1)
end

def git_dir
  $git_dir ||= %x(git rev-parse --git-dir).sub(/\n$/,'')
end

def ref_to_hash ref
  %x(git rev-parse #{ref}).sub(/\n$/,'')
end

def hash_to_rev hash
  %x(git svn find-rev #{hash}).sub(/\n$/,'')
end

def ref_to_rev rev
  hash_to_rev( ref_to_hash(rev) )
end

def merge_from_svn ref, opts={}
  hash = ref_to_hash ref
  rev  = hash_to_rev hash
  branch_name = opts[:branch_name]
  message = opts[:message]
  unless branch_name
    if ref =~ /svn\//
      branch_name = ref.sub(/svn\//,'')
    else
      die %(can't find branch name)
    end
  end
  puts "#{ref} #{hash} #{rev} #{branch_name}"
  %x(git merge --no-commit --no-ff #{opts[:log] ? '--log' : ''} #{hash})

  old_msg_name = "#{git_dir}/MERGE_MSG"
  new_msg_name = "#{git_dir}/MERGE_MSG_tmp"

  File.open new_msg_name, "w" do |new_msg|
    first = true
    File.open old_msg_name do |old_msg|
      old_msg.each_line do |line|
        if first
          if message
            new_msg.puts message
          else
            new_msg.puts "Merge #{branch_name} (#{rev})"
          end
          first = false
        else
          new_msg.puts line.sub(/commit '#{hash}'/, branch_name)
        end
      end
    end
  end
  FileUtils.mv new_msg_name, old_msg_name
  %x(git commit #{opts[:edit_message] ? '' : "-F #{old_msg_name}"})
end


ref = nil
opts = {}
args = ARGV.dup
while arg = args.shift
  case arg
  when /-h|--help/
    usage
  when /-b|--branch-name/
    if arg =~ /=/
      opts[:branch_name] = arg.sub(/.*=\s*/,'')
    else
      opts[:branch_name] = args.shift
    end
  when /-e|--edit-message/
    opts[:edit] = true
  when /-l|--log/
    opts[:log] = true
  when /-m|--message/
    if arg =~ /=/
      opts[:message] = arg.sub(/.*=\s*/,'')
    else
      opts[:message] = args.shift
    end
  when /^-/
    die "unknow option #{arg}", true
  else
    case
    when ref
      usage -1
    else
      ref = arg
    end
  end
end
usage -1 unless ref
merge_from_svn ref, opts