#!/usr/bin/env ruby

########################################################################################################

# Usage: #

# gitopendiff [-r<left rev>:<right-rev>] [repository] #

# #

# Example: #

# gitopendiff # == gitopendiff -rHEAD^:HEAD . #

# gitopendiff -rHEAD^^:HEAD # == gitopendiff -rHEAD^^:HEAD . #

# gitopendiff -master:origin/master # == gitopendiff -rmaster:origin/master . #

# gitopendiff /path/to/git/repository # == gitopendiff -rHEAD^:HEAD /path/to/git/repository #

# gitopendiff -rHEAD^:HEAD /path/to/git/repository # == gitopendiff -rHEAD^:HEAD /path/to/git/repository #

# #

# Authored by Simon Menke, with minor optimizations by Jonathan del Strother #

########################################################################################################

def checkout(origin, rev)

tmp = "/tmp/git_opendiff_#{rand}.tmp/"

Dir.mkdir(tmp)

Dir.chdir(origin) do

# The clean, porcelainy way would be "git archive --format=tar '#{rev}' | (cd #{tmp} && tar xf -)"

# I've found the plumbing to be marginally faster :

system "git read-tree '#{rev}'; git checkout-index --prefix=#{tmp} -a; git read-tree HEAD"

end

return tmp

end

def diff(origin, revs={})

revs = {:left=>"HEAD^",:right=>"HEAD"}.merge(revs)

left = checkout origin, revs[:left]

right = checkout origin, revs[:right]

system "opendiff '#{left}' '#{right}'"

end

revs = {}

git_dir = Dir.pwd

ARGV.each do |arg|

if arg[0,2] == "-r"

rev_strings = arg[2..-1].split(':')

case rev_strings.size

when 1

revs[:left] = rev_strings[0] unless rev_strings[0].empty?

when 2

revs[:left] = rev_strings[0] unless rev_strings[0].empty?

revs[:right] = rev_strings[1] unless rev_strings[1].empty?

else

revs = nil

end

else

git_dir = arg unless arg.empty?

end

end

diff(git_dir, revs)