# YBlog - Encapsulate git
Keywords: git, protection, branches, diverged

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# Encapsulate git

Here is a solution to maintain divergent branches in git. Because it is easy to merge by mistake. I give a script that encapsulate git in order to forbid some merge and warn you some merge should be dangerous.

## how to protect against your own dumb

I work on a project in which some of my git branches should remain divergent. And divergences should grow.

I also use some branch to contain what is common between projects.

Say I have some branches:

master: common to all branches dev: branch devoted to unstable development client: branch with features for all client but not general enough for master clientA: project adapted for client A clientB: project adapted for client B

Here how I want to work:

And more precisely the branch hierarchy:

An arrow from A to B means, you can merge A in B. If there is no arrow from A to B that means it is forbidden to merge A in B. Here is the corresponding rubycode:

`$architecture={ :master => [ :dev, :client ], :dev => [ :master ], :client => [ :clientA, :clientB ] }`

Having a `:master => [ :dev, :client ]` means you can merge `master` branch into `dev` and `client`.

If by mistake I make a `git checkout master && git merge clientA`, I made a mistake. This is why I made a script which encapsulate the git behaviour to dodge this kind of mistake.

But this script do far more than that. It also merge from top to down. The action `allmerges` will do:

`git co dev && git merge master git co client && git merge master git co clientA && git merge client git co clientB && git merge client`

That means, I can update all branches. The algorithm will not make loop even if there is a cycle in the branch hierarchy.

Here it is:

`#!/usr/bin/env ruby # encoding: utf-8`

# architecture

#

# master <-> dev

# master -> client

# clien -> clientA | clientB

#

# merge using two of these branches should be

# restricted to these rules

# merge to one of these branch and an unknown one should

# raise a warning, and may the option to add this new branch

# to the hierarchy

$architecture={ :master => [ :dev, :client ], :dev => [ :master ], :client => [ :clientA, :clientB ] }

def get_current_branch() (`git branch --no-color | awk '$1 == "*" {print $2}'`).chop.intern end

if ARGV.length == 0 puts %{usage: $0:t [git_command or local_command]

local commands: allmerges: merge from top to down} exit 0 end

require ‘set’ $known_branches=Set.new $architecture.each do |k,v| $known_branches.add(k) v.each { |b| $known_branches.add(b) } end

def rec_merge(branch) if $architecture[branch].nil? return end $architecture[branch].each do |b| if $flag.has_key?(b.to_s + branch.to_s) next end flagname=branch.to_s + b.to_s if $flag.has_key?(flagname) next end if system %{eng checkout #{b}} if get_current_branch != b puts “Can’t checkout to #{b}” exit 2 end if system %{eng merge #{branch}} $flag[flagname]=true rec_merge(b) else exit 1 end else exit 1 end end end

def do_all_merges puts ‘Will merge from father to sons’ current_branch=get_current_branch $flag={} rec_merge(:master) system %{git co #{current_branch}} end

def do_merge current_branch=get_current_branch src_branch=ARGV[1].intern puts %{do_merge: #{src_branch} => #{current_branch}} if $known_branches.include?(current_branch) if $known_branches.include?(src_branch) if $architecture.has_key?(src_branch) and $architecture[src_branch].include?(current_branch) system %{git merge #{src_branch}} else puts %{Forbidden merge: #{src_branch} => #{current_branch}} end else puts %{Warning! #{src_branch} not mentionned in rb configuration} sleep 2 system %{git merge #{src_branch}} puts %{Warning! #{src_branch} not mentionned in rb configuration} end end end

case ARGV[0] when ‘allmerges’ then do_all_merges when ‘merge’ then do_merge else system %{git #{ARGV.join(’ ’)}} end

All you need to do to make it work is simply to copy eng in a directory contained in your PATH.

Of course try to use as few as possible `cherry-pick` and `rebase`. This script was intended to work with workflow using `pull` and `merge`.

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Published on 2010-03-23
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Yann Esposito©
Done with Vim spacemacs & nanoc Hakyll

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