#!/usr/bin/python

# reisolate - re-isolate a patch
# this is used for taking a large patch, and dividing it into
# smaller pieces (based on previously existing smaller patches)
#
# This program is used to extract a sub-patch from a larger
# patch, based on the list of files in an existing patch.
# example: if patch L has diffs for files A, B, and C,
# and patch S has diffs for files A, and B, then
#     reisolate L S S-new
# will take the pieces of L for files A and B and put
# them into patch S-new. 
#
# usage: reisolate new.patch prior_sub.patch new_sub.patch
#

import sys
import os
import commands

def usage():
	print "usage: reisolate new.patch prior_sub.patch new_sub.patch"
	sys.exit(1)

def main():
	# get filenames from command line args
	try:
		patch = sys.argv[1]
		prior_sub = sys.argv[2]
		new_sub = sys.argv[3]
	except:
		usage()

	# parse the filenames to extract
	command = "diffinfo -l %s" % prior_sub
	sub_file_lines = commands.getoutput(command).split("\n")
	sub_file_list = []
	for line in sub_file_lines:
		sub_file_list.append(line.strip())

	# get rid of new sub-patch, if it exists
	try:
		os.unlink(new_sub)
	except:
		pass

	# put each sub-sub-patch into a separate file
	# (this is only done for debugging purposes)
	tc = 1
	# extract each file and append to new_sub
	for f in sub_file_list:
		print "extracting", f
		tempfile = "reisolate.tmp%03d" % tc
		command = "diffinfo -p ^%(f)s -n %(tempfile)s %(patch)s" % locals()
		(status,output) = commands.getstatusoutput(command)
		command = "cat %(tempfile)s >>%(new_sub)s" % locals()
		(status,output) = commands.getstatusoutput(command)
		tc += 1
		os.unlink(tempfile)

	print "new sub-patch is:", new_sub

if __name__=="__main__":
	main()