Example Scripts from Three Trees Talk

auto-backup.rb

back_branch = 'refs/heads/backup'

`rm /tmp/backup_index`
ENV['GIT_INDEX_FILE'] = '/tmp/backup_index'

last_commit = `git rev-parse #{back_branch}`.strip
last_tree   = `git rev-parse #{back_branch}^{tree}`.strip

`git add --all`
next_tree = `git write-tree`.strip

if last_tree != next_tree
  extra = last_commit.size == 40 ? "-p #{last_commit}" : ''
  csha = `echo 'back' | git commit-tree #{next_tree} #{extra}`
  `git update-ref #{back_branch} #{csha}`
end

doc-publish.rb

task :publish_docs do
  `rocco libgit.rb` # creates libgit.html
  ENV['GIT_INDEX_FILE'] = '/tmp/i'
  `git add -f libgit.html`
  tsha = `git write-tree`
  csha = `echo 'boom' | git commit-tree #{tsha}`
  `git update-ref refs/heads/gh-pages #{csha}`
  `git push -f origin gh-pages`
end

freeze-submodules.rb

current_commit = `git rev-parse HEAD`
current_tree = `git rev-parse HEAD^{tree}`

# get a list of submodules
status = `git submodule status`.chomp
subdata = status.split("\n")
subdata.each do |subline|
  sharaw, path = subline.split(" ")
  sha = sharaw[1, sharaw.size - 1]
  remote = path.gsub('/', '-')
  `git remote add #{remote} #{path} 2>/dev/null` # fetch each submodule into a remote
  `git fetch #{remote}`
  `git read-tree --prefix=#{path} #{sha}` # for each submodule/sha, read-tree the sha into the path
end

# find heroku parent
prev_commit = `git rev-parse heroku 2>/dev/null`.chomp  
pcommit = (prev_commit != "heroku") ? "-p #{prev_commit}" : ''

# write-tree/commit-tree with message of what commit sha it's based on
tree_sha = `git write-tree`.chomp
commit_sha = `echo "deploy at #{current_commit}" | git commit-tree #{tree_sha} #{pcommit}`

# update-ref
`git update-ref refs/heads/heroku #{commit_sha}`

# reset
`git reset HEAD`

rebase.rb

#! /usr/bin/env ruby

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

# 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 HEAD > /tmp/#{sha}.p`
end

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

# 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!"
end

subproj-tarball.rb

`rm /tmp/in`
ENV['GIT_INDEX_FILE'] = '/tmp/in'
`git read-tree --prefix lib   master:lib`
`git read-tree --prefix ext-m extras:ext`
tsha = `git write-tree`
`git archive --format=zip -o out.zip #{tsha}`