server/git.py

#
# Copyright 2007 IBM Corp. Released under the GPL v2
# Authors: Ryan Harper <ryanh@us.ibm.com>
#

"""
This module defines a class for handling building from git repos
"""

__author__ = """
ryanh@us.ibm.com (Ryan Harper)
"""


import os
import urllib2

from common.error import *
import utils
from utils import *
import installable_object

class GitRepo(installable_object.InstallableObject):
	"""
	This class represents a git repo.

	It is used to pull down a local copy of a git repo, check if the local
	repo is up-to-date, if not update.  It delegates the install to
	implementation classes.

	"""

	def __init__(self, repodir, giturl, weburl):
		super(installable_object.InstallableObject, self).__init__()
		if repodir == None:
			raise "You must provide a directory to hold the git repository"
		self.repodir = sh_escape(repodir)
		if giturl == None:
			raise "You must provide a git URL to the repository"
		self.giturl = giturl
		if weburl == None:
			raise "You must provide a http URL to the repository"
		self.weburl = weburl

		# path to .git dir
		self.gitpath = sh_escape(os.path.join(self.repodir,'.git'))

		# base git command , pointing to gitpath git dir
		self.gitcmdbase = 'git --git-dir=%s' % self.gitpath

		# default to same remote path as local
		self.__build = os.path.dirname(self.repodir)


	def run(self, command, timeout=None, ignore_status=False):
		return utils.run(r'%s' % (utils.sh_escape(command)),
                                  timeout, ignore_status)


	# base install method
	def install(self, host, builddir=None):
		# allow override of target remote dir
		if builddir:
			self.__build = builddir

		# push source to host for install
		print 'pushing %s to host:%s' %(self.source_material, self.__build)
		host.send_file(self.source_material, self.__build)


	def gitcmd(self, cmd, ignore_status=False):
		return self.run('%s %s'%(self.gitcmdbase, cmd),
						ignore_status=ignore_status)


	def get(self, **kwargs):
		"""
		This method overrides baseclass get so we can do proper git 
		clone/pulls, and check for updated versions.  The result of
		this method will leave an up-to-date version of git repo at
		'giturl' in 'repodir' directory to be used by build/install
		methods.
		"""

		if not self.is_repo_initialized():
			# this is your first time ...
			print 'cloning repo...'
			cmd = 'clone %s %s ' %(self.giturl, self.repodir)
			rv = self.gitcmd(cmd, True)
			if rv.exit_status != 0:
				print rv.stderr
				raise "Failed to clone git url"
			else:
				print rv.stdout

		else:
			# exiting repo, check if we're up-to-date
			if self.is_out_of_date():
				print 'updating repo...'
				rv = self.gitcmd('pull', True)
				if rv.exit_status != 0:
					print rv.stderr
					raise "Failed to pull git repo data"
			else:
				print 'repo up-to-date'


		# remember where the source is
		self.source_material = self.repodir


	def get_local_head(self):
		cmd = 'log --max-count=1'
		gitlog = self.gitcmd(cmd).stdout

		# parsing the commit checksum out of git log 's first entry.
		# Output looks like:
		# 	
		# 	commit 1dccba29b4e5bf99fb98c324f952386dda5b097f
		# 	Merge: 031b69b... df6af41...
		# 	Author: Avi Kivity <avi@qumranet.com>
		# 	Date:   Tue Oct 23 10:36:11 2007 +0200
		#
		# 	    Merge home:/home/avi/kvm/linux-2.6
		return str(gitlog.split('\n')[0]).split()[1]


	def get_remote_head(self):
		def __needs_refresh(lines):
			tag = '<meta http-equiv="refresh" content="0"/>'
			if len(filter(lambda x: x.startswith(tag), lines)) > 0:
				return True

			return False


		# scan git web interface for revision HEAD's commit tag
		gitwebaction=';a=commit;h=HEAD'
		url = self.weburl+gitwebaction
		max_refresh = 4
		r = 0

		print 'checking %s for changes' %(url)
		u = urllib2.urlopen(url)
		lines = u.read().split('\n')

		while __needs_refresh(lines) and r < max_refresh:
			print 'refreshing url'
			r = r+1
			u = urllib2.urlopen(url)
			lines = u.read().split('\n')

		if r >= max_refresh:
			raise 'Failed to get remote repo status'

		# looking for a line like:
		# <tr><td>commit</td><td # class="sha1">aadea67210c8b9e7a57744a1c2845501d2cdbac7</td></tr>
		commit_filter = lambda x: x.startswith('<tr><td>commit</td>')
		commit_line = filter(commit_filter, lines)

		# extract the sha1 sum from the commit line
		return str(commit_line).split('>')[4].split('<')[0]


	def is_out_of_date(self):
		local_head = self.get_local_head()
		remote_head = self.get_remote_head()

		# local is out-of-date, pull
		if local_head != remote_head:
			return True

		return False


	def is_repo_initialized(self):
		# if we fail to get a rv of 0 out of the git log command
		# then the repo is bogus

		cmd = 'log --max-count=1'
		rv = self.gitcmd(cmd, True)
		if rv.exit_status == 0:
			return True

		return False