Allow the lastchange target to get a hard-coded default last change...

build/util/lastchange.py

 #!/usr/bin/env python
 # Copyright (c) 2009 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.
 
 """
 lastchange.py -- Chromium revision fetching utility.
 """
 
 import optparse
@@ skipping 42 matching lines @@
     return None
   id = None
   if p:
     git_re = re.compile('^\s*git-svn-id:\s+(\S+)@(\d+)', re.M)
     m = git_re.search(p.stdout.read())
     if m:
       id = m.group(2)
   return id
 
 
-def fetch_change():
+def fetch_change(default_lastchange):
   """
   Returns the last change, from some appropriate revision control system.
   """
   change = svn_fetch_revision()
   if not change and sys.platform in ('linux2',):
     change = git_fetch_id()
   if not change:
-    change = '0'
+    if default_lastchange and os.path.exists(default_lastchange):
+      change = open(default_lastchange, 'r').read().strip()
+    else:
+      change = '0'
   return change
 
 
 def write_if_changed(file_name, contents):
   """
   Writes the specified contents to the specified file_name
   iff the contents are different than the current contents.
   """
   try:
     old_contents = open(file_name, 'r').read()
   except EnvironmentError:
     pass
   else:
     if contents == old_contents:
       return
     os.unlink(file_name)
   open(file_name, 'w').write(contents)
 
 
 def main(argv=None):
   if argv is None:
     argv = sys.argv
 
   parser = optparse.OptionParser(usage="lastchange.py [-h] [[-o] FILE]")
+  parser.add_option("-d", "--default-lastchange", metavar="FILE",
+                    help="default last change input FILE")
   parser.add_option("-o", "--output", metavar="FILE",
                     help="write last change to FILE")
   opts, args = parser.parse_args(argv[1:])
 
   out_file = opts.output
 
   while len(args) and out_file is None:
     if out_file is None:
       out_file = args.pop(0)
   if args:
     sys.stderr.write('Unexpected arguments: %r\n\n' % args)
     parser.print_help()
     sys.exit(2)
 
-  change = fetch_change()
+  change = fetch_change(opts.default_lastchange)
 
   contents = "LASTCHANGE=%s\n" % change
 
   if out_file:
     write_if_changed(out_file, contents)
   else:
     sys.stdout.write(contents)
 
   return 0
 
 
 if __name__ == '__main__':
   sys.exit(main())