Add bisect-builds.py help text discussing revisions.

tools/bisect-builds.py

 #!/usr/bin/env python
 # 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.
 
 """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 569 matching lines @@
   try:
     # Location of the latest build revision number
     return int(urllib.urlopen(url).read())
   except Exception, e:
     print('Could not determine latest revision. This could be bad...')
     return 999999999
 
 
 def main():
   usage = ('%prog [options] [-- chromium-options]\n'
-           'Perform binary search on the snapshot builds to find a minimal '
-           'range of revisions where a behavior change happened. The '
-           'behaviors are described as "good" and "bad". '
-           'It is NOT assumed that the behavior of the later revision is '
+           'Perform binary search on the snapshot builds to find a minimal\n'
+           'range of revisions where a behavior change happened. The\n'
+           'behaviors are described as "good" and "bad".\n'
+           'It is NOT assumed that the behavior of the later revision is\n'
            'the bad one.\n'
            '\n'
+           'Revision numbers should use\n'
+           '  Official versions (e.g. 1.0.1000.0) for official builds. (-o)\n'
+           '  SVN revisions (e.g. 123456) for chromium builds, from trunk.\n'
+           '    Use base_trunk_revision from http://omahaproxy.appspot.com/\n'
+           '    for earlier revs.\n'
+           '    Chrome\'s about: build number and omahaproxy branch_revision\n'
+           '    are incorrect, they are from branches.\n'
+           '\n'
            'Tip: add "-- --no-first-run" to bypass the first run prompts.')
   parser = optparse.OptionParser(usage=usage)
   # Strangely, the default help output doesn't include the choice list.
   choices = ['mac', 'win', 'linux', 'linux64']
             # linux-chromiumos lacks a continuous archive http://crbug.com/78158
   parser.add_option('-a', '--archive',
                     choices = choices,
                     help = 'The buildbot archive to bisect [%s].' %
                            '|'.join(choices))
   parser.add_option('-o', action="store_true", dest='official_builds',
@@ skipping 74 matching lines @@
     print 'WEBKIT CHANGELOG URL:'
     print '  ' + WEBKIT_CHANGELOG_URL % (max_webkit_rev, min_webkit_rev)
   print 'CHANGELOG URL:'
   if opts.official_builds:
     print OFFICIAL_CHANGELOG_URL % (min_chromium_rev, max_chromium_rev)
   else:
     print '  ' + CHANGELOG_URL % (min_chromium_rev, max_chromium_rev)
 
 if __name__ == '__main__':
   sys.exit(main())