Git script to rebase all child branches following a command

25 September, 2012

This script looks at the current status of the DAG to find the children of the current branch, runs an action, then rebases those children. It is particularly useful for users of git-svn, who may find themselves having to rebase all topic branches (and sub-topics which build off those) every time they git svn rebase or git svn dcommit.

For pure git projects, this is considered by many to be bad form, so use with discretion. People who like a linear history might like it.

I expect the script, in its current state, will fail in cases where the rebase can’t be done automatically, but for simple day-to-day operations it makes git-svn that bit less painful to use :-)

#!/usr/bin/ruby
 
#GistID: 3779324
 
require 'escape'
 
exit if ARGV.empty?
 
current_branch = `git symbolic-ref -q HEAD`.sub(/^refs\/heads\//, "").strip
 
exit if current_branch.empty?
 
def branch_output_to_array(output)
 
output.gsub(/^[ *]*/, "").split("\n").collect{ |e| e.strip }
 
end
 
IGNORED_BRANCHES = branch_output_to_array(`git branch --no-color -r`) << "HEAD"
 
def branches_on(commit)
 
ignored = IGNORED_BRANCHES << commit
 
log = `git log --pretty=%d --simplify-by-decoration #{commit} | head -n 1`
 
branches = log.sub(/^ \(([^)]+)\).*$/, '\1').split(", ")
 
branches.collect{ |e| e.strip }.reject{ |b| ignored.include? b }
 
end
 
def children_of(branch)
 
c = branch_output_to_array(`git branch --no-color --contains #{branch}`)
 
c.reject!{ |b| b == branch }
 
grandchildren = c.collect{|c| children_of c}.flatten
 
c.reject{ |b| grandchildren.include? b }
 
end
 
def branch_tree_from(branch)
 
siblings = branches_on branch
 
children = children_of(branch).reject{|c| siblings.include? c}
 
tail = siblings.collect{|s| [s]} + children.collect{|c| branch_tree_from(c)}
 
tail.empty? ? [branch] : [branch, tail]
 
end
 
def rebase_all_children(tree)
 
parent = tree.shift
 
children = tree.shift
 
children.map do |e|
 
system "git rebase #{parent} #{e.first}"
 
if e.size > 1
 
rebase_all_children e
 
end
 
end
 
end
 
initial_tree = branch_tree_from current_branch
 
if system "git #{Escape.shell_command(ARGV)}"
 
rebase_all_children initial_tree
 
system "git checkout #{current_branch}"
 
end

I have an alias set up to invoke it with git rar (“Run and Rebase”), so that I can type, for example, git rar svn rebase.

alias, git, git-svn, ruby, scripts