simple rebase

rebase.rb

#! /usr/bin/env ruby

# take a branch and rebase the current one onto it
branch_target = branch_onto = ARGV[0]
raise 'no target' unless branch_target

branch_onto = ARGV[1] if ARGV[1]

# record where we are and what branch we're on
branch_current = `git symbolic-ref HEAD`.chomp
sha_current = `git rev-parse #{branch_current}`.chomp

# ensure clean wd
raise 'not clean' unless `git status -s`.chomp == ''

# figure out the patch series
commits = `git rev-list #{branch_current} ^#{branch_target}`.chomp
shas = commits.split("\n").reverse

raise 'no commits' unless shas.size > 0

# extract all the patches
shas.each do |sha|
  puts "Extracting patch for #{sha}"
  `git show --format=email #{sha} > /tmp/#{sha}.p`
end

# reset to the new branch
`git reset --hard #{branch_onto}`

# apply all the patches
cool = true
shas.each do |sha|
  puts "Applying patch for #{sha}"
  `git am /tmp/#{sha}.p`
  if $?.exitstatus != 0
    cool = false
    break
  end
end

# reset if anything goes wrong
if !cool
  puts "Rebase failed, rolling back..."
  `git am --abort`
  `git reset --hard #{sha_current}`
else
  puts "Rebase succeeded! (if you need to revert, old sha was #{sha_current})"
end