gclient_scm.py

# Copyright (c) 2010 The Chromium Authors. All rights reserved.
# Use of this source code is governed by a BSD-style license that can be
# found in the LICENSE file.

"""Gclient-specific SCM-specific operations."""

import logging
import os
import posixpath
import re
import subprocess
import time

import scm
import gclient_utils


class DiffFilterer(object):
  """Simple class which tracks which file is being diffed and
  replaces instances of its file name in the original and
  working copy lines of the svn/git diff output."""
  index_string = "Index: "
  original_prefix = "--- "
  working_prefix = "+++ "

  def __init__(self, relpath):
    # Note that we always use '/' as the path separator to be
    # consistent with svn's cygwin-style output on Windows
    self._relpath = relpath.replace("\\", "/")
    self._current_file = ""
    self._replacement_file = ""

  def SetCurrentFile(self, current_file):
    self._current_file = current_file
    # Note that we always use '/' as the path separator to be
    # consistent with svn's cygwin-style output on Windows
    self._replacement_file = posixpath.join(self._relpath, current_file)

  def ReplaceAndPrint(self, line):
    print(line.replace(self._current_file, self._replacement_file))

  def Filter(self, line):
    if (line.startswith(self.index_string)):
      self.SetCurrentFile(line[len(self.index_string):])
      self.ReplaceAndPrint(line)
    else:
      if (line.startswith(self.original_prefix) or
          line.startswith(self.working_prefix)):
        self.ReplaceAndPrint(line)
      else:
        print line


### SCM abstraction layer

# Factory Method for SCM wrapper creation

def GetScmName(url):
  if url:
    url, _ = gclient_utils.SplitUrlRevision(url)
    if (url.startswith('git://') or url.startswith('ssh://') or
        url.endswith('.git')):
      return 'git'
    elif (url.startswith('http://') or url.startswith('https://') or
          url.startswith('svn://') or url.startswith('svn+ssh://')):
      return 'svn'
  return None


def CreateSCM(url, root_dir=None, relpath=None):
  SCM_MAP = {
    'svn' : SVNWrapper,
    'git' : GitWrapper,
  }

  scm_name = GetScmName(url)
  if not scm_name in SCM_MAP:
    raise gclient_utils.Error('No SCM found for url %s' % url)
  return SCM_MAP[scm_name](url, root_dir, relpath)


# SCMWrapper base class

class SCMWrapper(object):
  """Add necessary glue between all the supported SCM.

  This is the abstraction layer to bind to different SCM.
  """
  def __init__(self, url=None, root_dir=None, relpath=None):
    self.url = url
    self._root_dir = root_dir
    if self._root_dir:
      self._root_dir = self._root_dir.replace('/', os.sep)
    self.relpath = relpath
    if self.relpath:
      self.relpath = self.relpath.replace('/', os.sep)
    if self.relpath and self._root_dir:
      self.checkout_path = os.path.join(self._root_dir, self.relpath)

  def RunCommand(self, command, options, args, file_list=None):
    # file_list will have all files that are modified appended to it.
    if file_list is None:
      file_list = []

    commands = ['cleanup', 'export', 'update', 'updatesingle', 'revert',
                'revinfo', 'status', 'diff', 'pack', 'runhooks']

    if not command in commands:
      raise gclient_utils.Error('Unknown command %s' % command)

    if not command in dir(self):
      raise gclient_utils.Error('Command %s not implemented in %s wrapper' % (
          command, self.__class__.__name__))

    return getattr(self, command)(options, args, file_list)


class GitWrapper(SCMWrapper):
  """Wrapper for Git"""

  @staticmethod
  def cleanup(options, args, file_list):
    """'Cleanup' the repo.

    There's no real git equivalent for the svn cleanup command, do a no-op.
    """

  def diff(self, options, args, file_list):
    merge_base = self._Run(['merge-base', 'HEAD', 'origin'])
    self._Run(['diff', merge_base], redirect_stdout=False)

  def export(self, options, args, file_list):
    """Export a clean directory tree into the given path.

    Exports into the specified directory, creating the path if it does
    already exist.
    """
    assert len(args) == 1
    export_path = os.path.abspath(os.path.join(args[0], self.relpath))
    if not os.path.exists(export_path):
      os.makedirs(export_path)
    self._Run(['checkout-index', '-a', '--prefix=%s/' % export_path],
              redirect_stdout=False)

  def pack(self, options, args, file_list):
    """Generates a patch file which can be applied to the root of the
    repository.

    The patch file is generated from a diff of the merge base of HEAD and
    its upstream branch.
    """
    path = os.path.join(self._root_dir, self.relpath)
    merge_base = self._Run(['merge-base', 'HEAD', 'origin'])
    command = ['diff', merge_base]
    filterer = DiffFilterer(self.relpath)
    scm.GIT.RunAndFilterOutput(command, path, False, False, filterer.Filter)

  def update(self, options, args, file_list):
    """Runs git to update or transparently checkout the working copy.

    All updated files will be appended to file_list.

    Raises:
      Error: if can't get URL for relative path.
    """

    if args:
      raise gclient_utils.Error("Unsupported argument(s): %s" % ",".join(args))

    self._CheckMinVersion("1.6.6")

    default_rev = "refs/heads/master"
    url, deps_revision = gclient_utils.SplitUrlRevision(self.url)
    rev_str = ""
    revision = deps_revision
    if options.revision:
      # Override the revision number.
      revision = str(options.revision)
    if not revision:
      revision = default_rev

    rev_str = ' at %s' % revision
    files = []

    printed_path = False
    verbose = []
    if options.verbose:
      print("\n_____ %s%s" % (self.relpath, rev_str))
      verbose = ['--verbose']
      printed_path = True

    if revision.startswith('refs/heads/'):
      rev_type = "branch"
    elif revision.startswith('origin/'):
      # For compatability with old naming, translate 'origin' to 'refs/heads'
      revision = revision.replace('origin/', 'refs/heads/')
      rev_type = "branch"
    else:
      # hash is also a tag, only make a distinction at checkout
      rev_type = "hash"

    if not os.path.exists(self.checkout_path):
      self._Clone(revision, url, options.verbose)
      files = self._Run(['ls-files']).split()
      file_list.extend([os.path.join(self.checkout_path, f) for f in files])
      if not verbose:
        # Make the output a little prettier. It's nice to have some whitespace
        # between projects when cloning.
        print ""
      return

    if not os.path.exists(os.path.join(self.checkout_path, '.git')):
      raise gclient_utils.Error('\n____ %s%s\n'
                                '\tPath is not a git repo. No .git dir.\n'
                                '\tTo resolve:\n'
                                '\t\trm -rf %s\n'
                                '\tAnd run gclient sync again\n'
                                % (self.relpath, rev_str, self.relpath))

    cur_branch = self._GetCurrentBranch()

    # Cases:
    # 0) HEAD is detached. Probably from our initial clone.
    #   - make sure HEAD is contained by a named ref, then update.
    # Cases 1-4. HEAD is a branch.
    # 1) current branch is not tracking a remote branch (could be git-svn)
    #   - try to rebase onto the new hash or branch
    # 2) current branch is tracking a remote branch with local committed
    #    changes, but the DEPS file switched to point to a hash
    #   - rebase those changes on top of the hash
    # 3) current branch is tracking a remote branch w/or w/out changes,
    #    no switch
    #   - see if we can FF, if not, prompt the user for rebase, merge, or stop
    # 4) current branch is tracking a remote branch, switches to a different
    #    remote branch
    #   - exit

    # GetUpstreamBranch returns something like 'refs/remotes/origin/master' for
    # a tracking branch
    # or 'master' if not a tracking branch (it's based on a specific rev/hash)
    # or it returns None if it couldn't find an upstream
    if cur_branch is None:
      upstream_branch = None
      current_type = "detached"
      logging.debug("Detached HEAD")
    else:
      upstream_branch = scm.GIT.GetUpstreamBranch(self.checkout_path)
      if not upstream_branch or not upstream_branch.startswith('refs/remotes'):
        current_type = "hash"
        logging.debug("Current branch is not tracking an upstream (remote)"
                      " branch.")
      elif upstream_branch.startswith('refs/remotes'):
        current_type = "branch"
      else:
        raise gclient_utils.Error('Invalid Upstream: %s' % upstream_branch)

    # Update the remotes first so we have all the refs.
    for _ in range(10):
      try:
        if rev_type == "branch":
          remote_output, remote_err = scm.GIT.Capture(
            ['fetch'] + verbose + ['origin', revision],
            self.checkout_path,
            print_error=False)
        else:
          remote_output, remote_err = scm.GIT.Capture(
            ['remote'] + verbose + ['update'],
            self.checkout_path,
            print_error=False)
        break
      except gclient_utils.CheckCallError, e:
        # Hackish but at that point, git is known to work so just checking for
        # 502 in stderr should be fine.
        if '502' in e.stderr:
          print str(e)
          print "Sleeping 15 seconds and retrying..."
          time.sleep(15)
          continue
        raise

    if verbose:
      print remote_output.strip()
      # git remote update prints to stderr when used with --verbose
      print remote_err.strip()

    # This is a big hammer, debatable if it should even be here...
    if options.force or options.reset:
      self._Run(['reset', '--hard', 'HEAD'], redirect_stdout=False)

    if current_type == 'detached':
      # case 0
      self._CheckClean(rev_str)
      self._CheckDetachedHead(rev_str)
      self._Run(['checkout', '--quiet', '%s^0' % revision])
      if not printed_path:
        print("\n_____ %s%s" % (self.relpath, rev_str))
    elif current_type == 'hash':
      # case 1
      if scm.GIT.IsGitSvn(self.checkout_path) and upstream_branch is not None:
        # Our git-svn branch (upstream_branch) is our upstream
        self._AttemptRebase(upstream_branch, files, verbose=options.verbose,
                            newbase=revision, printed_path=printed_path)
        printed_path = True
      else:
        # Can't find a merge-base since we don't know our upstream. That makes
        # this command VERY likely to produce a rebase failure. For now we
        # assume origin is our upstream since that's what the old behavior was.
        upstream_branch = 'origin'
        if options.revision or deps_revision:
          upstream_branch = revision
        self._AttemptRebase(upstream_branch, files=files,
                            verbose=options.verbose, printed_path=printed_path)
        printed_path = True
    elif rev_type == 'hash':
      # case 2
      self._AttemptRebase(upstream_branch, files, verbose=options.verbose,
                          newbase=revision, printed_path=printed_path)
      printed_path = True
    elif revision.replace('heads', 'remotes/origin') != upstream_branch:
      # case 4
      new_base = revision.replace('heads', 'remotes/origin')
      if not printed_path:
        print("\n_____ %s%s" % (self.relpath, rev_str))
      switch_error = ("Switching upstream branch from %s to %s\n"
                     % (upstream_branch, new_base) +
                     "Please merge or rebase manually:\n" +
                     "cd %s; git rebase %s\n" % (self.checkout_path, new_base) +
                     "OR git checkout -b <some new branch> %s" % new_base)
      raise gclient_utils.Error(switch_error)
    else:
      # case 3 - the default case
      files = self._Run(['diff', upstream_branch, '--name-only']).split()
      if verbose:
        print "Trying fast-forward merge to branch : %s" % upstream_branch
      try:
        merge_output, merge_err = scm.GIT.Capture(['merge', '--ff-only',
                                                   upstream_branch],
                                                  self.checkout_path,
                                                  print_error=False)
      except gclient_utils.CheckCallError, e:
        if re.match('fatal: Not possible to fast-forward, aborting.', e.stderr):
          if not printed_path:
            print("\n_____ %s%s" % (self.relpath, rev_str))
            printed_path = True
          while True:
            try:
              action = str(raw_input("Cannot fast-forward merge, attempt to "
                                     "rebase? (y)es / (q)uit / (s)kip : "))
            except ValueError:
              gclient_utils.Error('Invalid Character')
              continue
            if re.match(r'yes|y', action, re.I):
              self._AttemptRebase(upstream_branch, files,
                                  verbose=options.verbose,
                                  printed_path=printed_path)
              printed_path = True
              break
            elif re.match(r'quit|q', action, re.I):
              raise gclient_utils.Error("Can't fast-forward, please merge or "
                                        "rebase manually.\n"
                                        "cd %s && git " % self.checkout_path
                                        + "rebase %s" % upstream_branch)
            elif re.match(r'skip|s', action, re.I):
              print "Skipping %s" % self.relpath
              return
            else:
              print "Input not recognized"
        elif re.match("error: Your local changes to '.*' would be "
                      "overwritten by merge.  Aborting.\nPlease, commit your "
                      "changes or stash them before you can merge.\n",
                      e.stderr):
          if not printed_path:
            print("\n_____ %s%s" % (self.relpath, rev_str))
            printed_path = True
          raise gclient_utils.Error(e.stderr)
        else:
          # Some other problem happened with the merge
          logging.error("Error during fast-forward merge in %s!" % self.relpath)
          print e.stderr
          raise
      else:
        # Fast-forward merge was successful
        if not re.match('Already up-to-date.', merge_output) or verbose:
          if not printed_path:
            print("\n_____ %s%s" % (self.relpath, rev_str))
            printed_path = True
          print merge_output.strip()
          if merge_err:
            print "Merge produced error output:\n%s" % merge_err.strip()
          if not verbose:
            # Make the output a little prettier. It's nice to have some
            # whitespace between projects when syncing.
            print ""

    file_list.extend([os.path.join(self.checkout_path, f) for f in files])

    # If the rebase generated a conflict, abort and ask user to fix
    if self._IsRebasing():
      raise gclient_utils.Error('\n____ %s%s\n'
                                '\nConflict while rebasing this branch.\n'
                                'Fix the conflict and run gclient again.\n'
                                'See man git-rebase for details.\n'
                                % (self.relpath, rev_str))

    if verbose:
      print "Checked out revision %s" % self.revinfo(options, (), None)

  def revert(self, options, args, file_list):
    """Reverts local modifications.

    All reverted files will be appended to file_list.
    """
    path = os.path.join(self._root_dir, self.relpath)
    if not os.path.isdir(path):
      # revert won't work if the directory doesn't exist. It needs to
      # checkout instead.
      print("\n_____ %s is missing, synching instead" % self.relpath)
      # Don't reuse the args.
      return self.update(options, [], file_list)

    default_rev = "refs/heads/master"
    _, deps_revision = gclient_utils.SplitUrlRevision(self.url)
    if not deps_revision:
      deps_revision = default_rev
    if deps_revision.startswith('refs/heads/'):
      deps_revision = deps_revision.replace('refs/heads/', 'origin/')

    files = self._Run(['diff', deps_revision, '--name-only']).split()
    self._Run(['reset', '--hard', deps_revision], redirect_stdout=False)
    file_list.extend([os.path.join(self.checkout_path, f) for f in files])

  def revinfo(self, options, args, file_list):
    """Display revision"""
    return self._Run(['rev-parse', 'HEAD'])

  def runhooks(self, options, args, file_list):
    self.status(options, args, file_list)

  def status(self, options, args, file_list):
    """Display status information."""
    if not os.path.isdir(self.checkout_path):
      print('\n________ couldn\'t run status in %s:\nThe directory '
            'does not exist.' % self.checkout_path)
    else:
      merge_base = self._Run(['merge-base', 'HEAD', 'origin'])
      self._Run(['diff', '--name-status', merge_base], redirect_stdout=False)
      files = self._Run(['diff', '--name-only', merge_base]).split()
      file_list.extend([os.path.join(self.checkout_path, f) for f in files])

  def FullUrlForRelativeUrl(self, url):
    # Strip from last '/'
    # Equivalent to unix basename
    base_url = self.url
    return base_url[:base_url.rfind('/')] + url

  def _Clone(self, revision, url, verbose=False):
    """Clone a git repository from the given URL.

    Once we've cloned the repo, we checkout a working branch if the specified
    revision is a branch head. If it is a tag or a specific commit, then we
    leave HEAD detached as it makes future updates simpler -- in this case the
    user should first create a new branch or switch to an existing branch before
    making changes in the repo."""
    if not verbose:
      # git clone doesn't seem to insert a newline properly before printing
      # to stdout
      print ""

    clone_cmd = ['clone']
    if revision.startswith('refs/heads/'):
      clone_cmd.extend(['-b', revision.replace('refs/heads/', '')])
      detach_head = False
    else:
      clone_cmd.append('--no-checkout')
      detach_head = True
    if verbose:
      clone_cmd.append('--verbose')
    clone_cmd.extend([url, self.checkout_path])

    for _ in range(3):
      try:
        self._Run(clone_cmd, cwd=self._root_dir, redirect_stdout=False)
        break
      except gclient_utils.Error, e:
        # TODO(maruel): Hackish, should be fixed by moving _Run() to
        # CheckCall().
        # Too bad we don't have access to the actual output.
        # We should check for "transfer closed with NNN bytes remaining to
        # read". In the meantime, just make sure .git exists.
        if (e.args[0] == 'git command clone returned 128' and
            os.path.exists(os.path.join(self.checkout_path, '.git'))):
          print str(e)
          print "Retrying..."
          continue
        raise e

    if detach_head:
      # Squelch git's very verbose detached HEAD warning and use our own
      self._Run(['checkout', '--quiet', '%s^0' % revision])
      print \
        "Checked out %s to a detached HEAD. Before making any commits\n" \
        "in this repo, you should use 'git checkout <branch>' to switch to\n" \
        "an existing branch or use 'git checkout origin -b <branch>' to\n" \
        "create a new branch for your work." % revision

  def _AttemptRebase(self, upstream, files, verbose=False, newbase=None,
                     branch=None, printed_path=False):
    """Attempt to rebase onto either upstream or, if specified, newbase."""
    files.extend(self._Run(['diff', upstream, '--name-only']).split())
    revision = upstream
    if newbase:
      revision = newbase
    if not printed_path:
      print "\n_____ %s : Attempting rebase onto %s..." % (self.relpath,
                                                           revision)
      printed_path = True
    else:
      print "Attempting rebase onto %s..." % revision

    # Build the rebase command here using the args
    # git rebase [options] [--onto <newbase>] <upstream> [<branch>]
    rebase_cmd = ['rebase']
    if verbose:
      rebase_cmd.append('--verbose')
    if newbase:
      rebase_cmd.extend(['--onto', newbase])
    rebase_cmd.append(upstream)
    if branch:
      rebase_cmd.append(branch)

    try:
      rebase_output, rebase_err = scm.GIT.Capture(rebase_cmd,
                                                  self.checkout_path,
                                                  print_error=False)
    except gclient_utils.CheckCallError, e:
      if re.match(r'cannot rebase: you have unstaged changes', e.stderr) or \
         re.match(r'cannot rebase: your index contains uncommitted changes',
                  e.stderr):
        while True:
          rebase_action = str(raw_input("Cannot rebase because of unstaged "
                                        "changes.\n'git reset --hard HEAD' ?\n"
                                        "WARNING: destroys any uncommitted "
                                        "work in your current branch!"
                                        " (y)es / (q)uit / (s)how : "))
          if re.match(r'yes|y', rebase_action, re.I):
            self._Run(['reset', '--hard', 'HEAD'], redirect_stdout=False)
            # Should this be recursive?
            rebase_output, rebase_err = scm.GIT.Capture(rebase_cmd,
                                                        self.checkout_path)
            break
          elif re.match(r'quit|q', rebase_action, re.I):
            raise gclient_utils.Error("Please merge or rebase manually\n"
                                      "cd %s && git " % self.checkout_path
                                      + "%s" % ' '.join(rebase_cmd))
          elif re.match(r'show|s', rebase_action, re.I):
            print "\n%s" % e.stderr.strip()
            continue
          else:
            gclient_utils.Error("Input not recognized")
            continue
      elif re.search(r'^CONFLICT', e.stdout, re.M):
        raise gclient_utils.Error("Conflict while rebasing this branch.\n"
                                  "Fix the conflict and run gclient again.\n"
                                  "See 'man git-rebase' for details.\n")
      else:
        print e.stdout.strip()
        print "Rebase produced error output:\n%s" % e.stderr.strip()
        raise gclient_utils.Error("Unrecognized error, please merge or rebase "
                                  "manually.\ncd %s && git " %
                                  self.checkout_path
                                  + "%s" % ' '.join(rebase_cmd))

    print rebase_output.strip()
    if rebase_err:
      print "Rebase produced error output:\n%s" % rebase_err.strip()
    if not verbose:
      # Make the output a little prettier. It's nice to have some
      # whitespace between projects when syncing.
      print ""

  @staticmethod
  def _CheckMinVersion(min_version):
    (ok, current_version) = scm.GIT.AssertVersion(min_version)
    if not ok:
      raise gclient_utils.Error('git version %s < minimum required %s' %
                                (current_version, min_version))

  def _IsRebasing(self):
    # Check for any of REBASE-i/REBASE-m/REBASE/AM. Unfortunately git doesn't
    # have a plumbing command to determine whether a rebase is in progress, so
    # for now emualate (more-or-less) git-rebase.sh / git-completion.bash
    g = os.path.join(self.checkout_path, '.git')
    return (
      os.path.isdir(os.path.join(g, "rebase-merge")) or
      os.path.isdir(os.path.join(g, "rebase-apply")))

  def _CheckClean(self, rev_str):
    # Make sure the tree is clean; see git-rebase.sh for reference
    try:
      scm.GIT.Capture(['update-index', '--ignore-submodules', '--refresh'],
                      self.checkout_path, print_error=False)
    except gclient_utils.CheckCallError:
      raise gclient_utils.Error('\n____ %s%s\n'
                                '\tYou have unstaged changes.\n'
                                '\tPlease commit, stash, or reset.\n'
                                  % (self.relpath, rev_str))
    try:
      scm.GIT.Capture(['diff-index', '--cached', '--name-status', '-r',
                       '--ignore-submodules', 'HEAD', '--'], self.checkout_path,
                       print_error=False)
    except gclient_utils.CheckCallError:
      raise gclient_utils.Error('\n____ %s%s\n'
                                '\tYour index contains uncommitted changes\n'
                                '\tPlease commit, stash, or reset.\n'
                                  % (self.relpath, rev_str))

  def _CheckDetachedHead(self, rev_str):
    # HEAD is detached. Make sure it is safe to move away from (i.e., it is
    # reference by a commit). If not, error out -- most likely a rebase is
    # in progress, try to detect so we can give a better error.
    try:
      _, _ = scm.GIT.Capture(
        ['name-rev', '--no-undefined', 'HEAD'],
        self.checkout_path,
        print_error=False)
    except gclient_utils.CheckCallError:
      # Commit is not contained by any rev. See if the user is rebasing:
      if self._IsRebasing():
        # Punt to the user
        raise gclient_utils.Error('\n____ %s%s\n'
                                  '\tAlready in a conflict, i.e. (no branch).\n'
                                  '\tFix the conflict and run gclient again.\n'
                                  '\tOr to abort run:\n\t\tgit-rebase --abort\n'
                                  '\tSee man git-rebase for details.\n'
                                   % (self.relpath, rev_str))
      # Let's just save off the commit so we can proceed.
      name = "saved-by-gclient-" + self._Run(["rev-parse", "--short", "HEAD"])
      self._Run(["branch", name])
      print ("\n_____ found an unreferenced commit and saved it as '%s'" % name)

  def _GetCurrentBranch(self):
    # Returns name of current branch or None for detached HEAD
    branch = self._Run(['rev-parse', '--abbrev-ref=strict', 'HEAD'])
    if branch == 'HEAD':
      return None
    return branch

  def _Run(self, args, cwd=None, redirect_stdout=True):
    # TODO(maruel): Merge with Capture or better gclient_utils.CheckCall().
    if cwd is None:
        cwd = self.checkout_path
    stdout = None
    if redirect_stdout:
      stdout = subprocess.PIPE
    if cwd == None:
      cwd = self.checkout_path
    cmd = [scm.GIT.COMMAND]
    cmd.extend(args)
    logging.debug(cmd)
    try:
      sp = subprocess.Popen(cmd, cwd=cwd, stdout=stdout)
      output = sp.communicate()[0]
    except OSError:
      raise gclient_utils.Error("git command '%s' failed to run." %
              ' '.join(cmd) + "\nCheck that you have git installed.")
    if sp.returncode:
      raise gclient_utils.Error('git command %s returned %d' %
                                (args[0], sp.returncode))
    if output is not None:
      return output.strip()


class SVNWrapper(SCMWrapper):
  """ Wrapper for SVN """

  def cleanup(self, options, args, file_list):
    """Cleanup working copy."""
    command = ['cleanup']
    command.extend(args)
    scm.SVN.Run(command, os.path.join(self._root_dir, self.relpath))

  def diff(self, options, args, file_list):
    # NOTE: This function does not currently modify file_list.
    path = os.path.join(self._root_dir, self.relpath)
    if not os.path.isdir(path):
      raise gclient_utils.Error('Directory %s is not present.' % path)
    command = ['diff']
    command.extend(args)
    scm.SVN.Run(command, path)

  def export(self, options, args, file_list):
    """Export a clean directory tree into the given path."""
    assert len(args) == 1
    export_path = os.path.abspath(os.path.join(args[0], self.relpath))
    try:
      os.makedirs(export_path)
    except OSError:
      pass
    assert os.path.exists(export_path)
    command = ['export', '--force', '.']
    command.append(export_path)
    scm.SVN.Run(command, os.path.join(self._root_dir, self.relpath))

  def pack(self, options, args, file_list):
    """Generates a patch file which can be applied to the root of the
    repository."""
    path = os.path.join(self._root_dir, self.relpath)
    if not os.path.isdir(path):
      raise gclient_utils.Error('Directory %s is not present.' % path)
    command = ['diff']
    command.extend(args)

    filterer = DiffFilterer(self.relpath)
    scm.SVN.RunAndFilterOutput(command, path, False, False, filterer.Filter)

  def update(self, options, args, file_list):
    """Runs svn to update or transparently checkout the working copy.

    All updated files will be appended to file_list.

    Raises:
      Error: if can't get URL for relative path.
    """
    # Only update if git is not controlling the directory.
    checkout_path = os.path.join(self._root_dir, self.relpath)
    git_path = os.path.join(self._root_dir, self.relpath, '.git')
    if os.path.exists(git_path):
      print("________ found .git directory; skipping %s" % self.relpath)
      return

    if args:
      raise gclient_utils.Error("Unsupported argument(s): %s" % ",".join(args))

    url, revision = gclient_utils.SplitUrlRevision(self.url)
    base_url = url
    forced_revision = False
    rev_str = ""
    if options.revision:
      # Override the revision number.
      revision = str(options.revision)
    if revision:
      forced_revision = True
      url = '%s@%s' % (url, revision)
      rev_str = ' at %s' % revision

    if not os.path.exists(checkout_path):
      # We need to checkout.
      command = ['checkout', url, checkout_path]
      command = self.AddAdditionalFlags(command, options, revision)
      scm.SVN.RunAndGetFileList(options, command, self._root_dir, file_list)
      return

    # Get the existing scm url and the revision number of the current checkout.
    from_info = scm.SVN.CaptureInfo(os.path.join(checkout_path, '.'), '.')
    if not from_info:
      raise gclient_utils.Error("Can't update/checkout %r if an unversioned "
                                "directory is present. Delete the directory "
                                "and try again." %
                                checkout_path)

    if options.manually_grab_svn_rev:
      # Retrieve the current HEAD version because svn is slow at null updates.
      if not revision:
        from_info_live = scm.SVN.CaptureInfo(from_info['URL'], '.')
        revision = str(from_info_live['Revision'])
        rev_str = ' at %s' % revision

    if from_info['URL'] != base_url:
      to_info = scm.SVN.CaptureInfo(url, '.')
      if not to_info.get('Repository Root') or not to_info.get('UUID'):
        # The url is invalid or the server is not accessible, it's safer to bail
        # out right now.
        raise gclient_utils.Error('This url is unreachable: %s' % url)
      can_switch = ((from_info['Repository Root'] != to_info['Repository Root'])
                    and (from_info['UUID'] == to_info['UUID']))
      if can_switch:
        print("\n_____ relocating %s to a new checkout" % self.relpath)
        # We have different roots, so check if we can switch --relocate.
        # Subversion only permits this if the repository UUIDs match.
        # Perform the switch --relocate, then rewrite the from_url
        # to reflect where we "are now."  (This is the same way that
        # Subversion itself handles the metadata when switch --relocate
        # is used.)  This makes the checks below for whether we
        # can update to a revision or have to switch to a different
        # branch work as expected.
        # TODO(maruel):  TEST ME !
        command = ["switch", "--relocate",
                   from_info['Repository Root'],
                   to_info['Repository Root'],
                   self.relpath]
        scm.SVN.Run(command, self._root_dir)
        from_info['URL'] = from_info['URL'].replace(
            from_info['Repository Root'],
            to_info['Repository Root'])
      else:
        if scm.SVN.CaptureStatus(checkout_path) and not options.force:
          raise gclient_utils.Error("Can't switch the checkout to %s; UUID "
                                    "don't match and there is local changes "
                                    "in %s. Delete the directory and "
                                    "try again." % (url, checkout_path))
        # Ok delete it.
        print("\n_____ switching %s to a new checkout" % self.relpath)
        gclient_utils.RemoveDirectory(checkout_path)
        # We need to checkout.
        command = ['checkout', url, checkout_path]
        command = self.AddAdditionalFlags(command, options, revision)
        scm.SVN.RunAndGetFileList(options, command, self._root_dir, file_list)
        return


    # If the provided url has a revision number that matches the revision
    # number of the existing directory, then we don't need to bother updating.
    if not options.force and str(from_info['Revision']) == revision:
      if options.verbose or not forced_revision:
        print("\n_____ %s%s" % (self.relpath, rev_str))
      return

    command = ["update", checkout_path]
    command = self.AddAdditionalFlags(command, options, revision)
    scm.SVN.RunAndGetFileList(options, command, self._root_dir, file_list)

  def updatesingle(self, options, args, file_list):
    checkout_path = os.path.join(self._root_dir, self.relpath)
    filename = args.pop()
    if scm.SVN.AssertVersion("1.5")[0]:
      if not os.path.exists(os.path.join(checkout_path, '.svn')):
        # Create an empty checkout and then update the one file we want.  Future
        # operations will only apply to the one file we checked out.
        command = ["checkout", "--depth", "empty", self.url, checkout_path]
        scm.SVN.Run(command, self._root_dir)
        if os.path.exists(os.path.join(checkout_path, filename)):
          os.remove(os.path.join(checkout_path, filename))
        command = ["update", filename]
        scm.SVN.RunAndGetFileList(options, command, checkout_path, file_list)
      # After the initial checkout, we can use update as if it were any other
      # dep.
      self.update(options, args, file_list)
    else:
      # If the installed version of SVN doesn't support --depth, fallback to
      # just exporting the file.  This has the downside that revision
      # information is not stored next to the file, so we will have to
      # re-export the file every time we sync.
      if not os.path.exists(checkout_path):
        os.makedirs(checkout_path)
      command = ["export", os.path.join(self.url, filename),
                 os.path.join(checkout_path, filename)]
      command = self.AddAdditionalFlags(command, options, options.revision)
      scm.SVN.Run(command, self._root_dir)

  def revert(self, options, args, file_list):
    """Reverts local modifications. Subversion specific.

    All reverted files will be appended to file_list, even if Subversion
    doesn't know about them.
    """
    path = os.path.join(self._root_dir, self.relpath)
    if not os.path.isdir(path):
      # svn revert won't work if the directory doesn't exist. It needs to
      # checkout instead.
      print("\n_____ %s is missing, synching instead" % self.relpath)
      # Don't reuse the args.
      return self.update(options, [], file_list)

    for file_status in scm.SVN.CaptureStatus(path):
      file_path = os.path.join(path, file_status[1])
      if file_status[0][0] == 'X':
        # Ignore externals.
        logging.info('Ignoring external %s' % file_path)
        continue

      if logging.getLogger().isEnabledFor(logging.INFO):
        logging.info('%s%s' % (file[0], file[1]))
      else:
        print(file_path)
      if file_status[0].isspace():
        logging.error('No idea what is the status of %s.\n'
                      'You just found a bug in gclient, please ping '
                      'maruel@chromium.org ASAP!' % file_path)
      # svn revert is really stupid. It fails on inconsistent line-endings,
      # on switched directories, etc. So take no chance and delete everything!
      try:
        if not os.path.exists(file_path):
          pass
        elif os.path.isfile(file_path) or os.path.islink(file_path):
          logging.info('os.remove(%s)' % file_path)
          os.remove(file_path)
        elif os.path.isdir(file_path):
          logging.info('gclient_utils.RemoveDirectory(%s)' % file_path)
          gclient_utils.RemoveDirectory(file_path)
        else:
          logging.error('no idea what is %s.\nYou just found a bug in gclient'
                        ', please ping maruel@chromium.org ASAP!' % file_path)
      except EnvironmentError:
        logging.error('Failed to remove %s.' % file_path)

    try:
      # svn revert is so broken we don't even use it. Using
      # "svn up --revision BASE" achieve the same effect.
      scm.SVN.RunAndGetFileList(options, ['update', '--revision', 'BASE'], path,
                                file_list)
    except OSError, e:
      # Maybe the directory disapeared meanwhile. We don't want it to throw an
      # exception.
      logging.error('Failed to update:\n%s' % str(e))

  def revinfo(self, options, args, file_list):
    """Display revision"""
    return scm.SVN.CaptureBaseRevision(self.checkout_path)

  def runhooks(self, options, args, file_list):
    self.status(options, args, file_list)

  def status(self, options, args, file_list):
    """Display status information."""
    path = os.path.join(self._root_dir, self.relpath)
    command = ['status']
    command.extend(args)
    if not os.path.isdir(path):
      # svn status won't work if the directory doesn't exist.
      print("\n________ couldn't run \'%s\' in \'%s\':\nThe directory "
            "does not exist."
            % (' '.join(command), path))
      # There's no file list to retrieve.
    else:
      scm.SVN.RunAndGetFileList(options, command, path, file_list)

  def FullUrlForRelativeUrl(self, url):
    # Find the forth '/' and strip from there. A bit hackish.
    return '/'.join(self.url.split('/')[:4]) + url

  @staticmethod
  def AddAdditionalFlags(command, options, revision):
    """Add additional flags to command depending on what options are set.
    command should be a list of strings that represents an svn command.

    This method returns a new list to be used as a command."""
    new_command = command[:]
    if revision:
      new_command.extend(['--revision', str(revision).strip()])
    # --force was added to 'svn update' in svn 1.5.
    if options.force and scm.SVN.AssertVersion("1.5")[0]:
      new_command.append('--force')
    return new_command