Check binary existence in gclient: 2nd try.

gclient_scm.py

 # Copyright (c) 2012 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
@@ skipping 67 matching lines @@
 
 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)
+  scm_class = SCM_MAP[scm_name]
+  if not scm_class.BinaryExists():
+    raise gclient_utils.Error('%s command not found' % scm_name)
+  return scm_class(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):
@@ skipping 27 matching lines @@
 
 class GitWrapper(SCMWrapper):
   """Wrapper for Git"""
 
   def __init__(self, url=None, root_dir=None, relpath=None):
     """Removes 'git+' fake prefix from git URL."""
     if url.startswith('git+http://') or url.startswith('git+https://'):
       url = url[4:]
     SCMWrapper.__init__(self, url, root_dir, relpath)
 
+  @staticmethod
+  def BinaryExists():
+    """Returns true if the command exists."""
+    try:
+      # We assume git is newer than 1.7.  See: crbug.com/114483
+      result, version = scm.GIT.AssertVersion('1.7')
+      if not result:
+        raise gclient_utils.Error('Git version is older than 1.7: %s' % version)
+      return result
+    except OSError:
+      return False
+
   def GetRevisionDate(self, revision):
     """Returns the given revision's date in ISO-8601 format (which contains the
     time zone)."""
     # TODO(floitsch): get the time-stamp of the given revision and not just the
     # time-stamp of the currently checked out revision.
     return self._Capture(['log', '-n', '1', '--format=%ai'])
 
   @staticmethod
   def cleanup(options, args, file_list):
     """'Cleanup' the repo.
@@ skipping 622 matching lines @@
     kwargs.setdefault('print_stdout', True)
     stdout = kwargs.get('stdout', sys.stdout)
     stdout.write('\n________ running \'git %s\' in \'%s\'\n' % (
                  ' '.join(args), kwargs['cwd']))
     gclient_utils.CheckCallAndFilter(['git'] + args, **kwargs)
 
 
 class SVNWrapper(SCMWrapper):
   """ Wrapper for SVN """
 
+  @staticmethod
+  def BinaryExists():
+    """Returns true if the command exists."""
+    try:
+      result, version = scm.SVN.AssertVersion('1.4')
+      if not result:
+        raise gclient_utils.Error('SVN version is older than 1.4: %s' % version)
+      return result
+    except OSError:
+      return False
+
   def GetRevisionDate(self, revision):
     """Returns the given revision's date in ISO-8601 format (which contains the
     time zone)."""
     date = scm.SVN.Capture(
         ['propget', '--revprop', 'svn:date', '-r', revision],
         os.path.join(self.checkout_path, '.'))
     return date.strip()
 
   def cleanup(self, options, args, file_list):
     """Cleanup working copy."""
@@ skipping 341 matching lines @@
       new_command.append('--force')
       if command[0] != 'checkout' and scm.SVN.AssertVersion('1.6')[0]:
         new_command.extend(('--accept', 'theirs-conflict'))
     elif options.manually_grab_svn_rev:
       new_command.append('--force')
       if command[0] != 'checkout' and scm.SVN.AssertVersion('1.6')[0]:
         new_command.extend(('--accept', 'postpone'))
     elif command[0] != 'checkout' and scm.SVN.AssertVersion('1.6')[0]:
       new_command.extend(('--accept', 'postpone'))
     return new_command