Bisect script should exit gracefully when not enough revisions are present...

build/build-bisect.py

 #!/usr/bin/python2.5
 # 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.
 
 """Snapshot Build Bisect Tool
 
 This script bisects a snapshot archive using binary search. It starts at
 a bad revision (it will try to guess HEAD) and asks for a last known-good
 revision. It will then binary search across this revision range by downloading,
@@ skipping 127 matching lines @@
 def AskIsGoodBuild(rev):
   """Annoyingly ask the user whether build |rev| is good or bad."""
   while True:
     check = raw_input("\nBuild %d is [(g)ood/(b)ad]: " % int(rev))[0]
     if (check == "g" or check  == "b"):
       return (check == "g")
     else:
       print("Just answer the question...")
 
 def main():
-  usage = ('%prog [options]\n'
+  usage = ('%prog [options] [-- chromium-options]\n'
            'Perform binary search on the snapshot builds.')
   parser = optparse.OptionParser(usage=usage)
   # Strangely, the default help output doesn't include the choice list.
   choices = ['mac', 'xp', 'linux', 'linux-64']
   parser.add_option('-a', '--archive',
                     choices = choices,
                     help = 'The buildbot archive to bisect [%s].' %
                            '|'.join(choices))
   parser.add_option('-b', '--bad', type = 'int',
                     help = 'The bad revision to bisect to.')
@@ skipping 40 matching lines @@
     good_rev = opts.good
   else:
     good_rev = 0
     try:
       good_rev = int(raw_input("Last known good [0]: "))
     except Exception, e:
       pass
 
   # Get a list of revisions to bisect across.
   revlist = GetRevList(good_rev, bad_rev)
+  if len(revlist) < 2:  # Don't have enough builds to bisect
+    print "We don't have enough builds to bisect. revlist: %s" % revlist
+    sys.exit(1)
 
   # If we don't have a |good_rev|, set it to be the first revision possible.
   if good_rev == 0:
     good_rev = revlist[0]
 
   # These are indexes of |revlist|.
   good = 0
   bad = len(revlist) - 1
   last_known_good_rev = revlist[good]
 
@@ skipping 24 matching lines @@
 
   # We're done. Let the user know the results in an official manner.
   print("You are probably looking for build %d." % revlist[bad])
   print("CHANGELOG URL:")
   print(CHANGELOG_URL % (last_known_good_rev, revlist[bad]))
   print("Built at revision:")
   print(BUILD_VIEWVC_URL % revlist[bad])
 
 if __name__ == '__main__':
   sys.exit(main())