git cl try: support multiple bots from different masters without specifying master.

git_cl.py

Index: git_cl.py
diff --git a/git_cl.py b/git_cl.py
index c78207bdc9ee4f1ab1541ec1ca74238d8621b377..f082d34db6168b1bec28efed9c01062ae6e3af05 100755
--- a/git_cl.py
+++ b/git_cl.py
@@ -4683,35 +4683,34 @@ def GetTreeStatusReason():
   return status['message']
 
 
-def GetBuilderMaster(bot_list):
-  """For a given builder, fetch the master from AE if available."""
+def GetBuilderMasters(bot_list):
+  """Returns a map of masters to builders for the given builders."""
   map_url = 'https://builders-map.appspot.com/'
   try:
-    master_map = json.load(urllib2.urlopen(map_url))
+    builders_map = json.load(urllib2.urlopen(map_url))
   except urllib2.URLError as e:
     return None, ('Failed to fetch builder-to-master map from %s. Error: %s.' %
                   (map_url, e))
   except ValueError as e:
     return None, ('Invalid json string from %s. Error: %s.' % (map_url, e))

[tandrii(chromium), 2016/10/23 17:00:02]

this Go-style error reporting makes me sad in Python every time i look :(

[qyearsley, 2016/10/24 21:33:39]

Yeah -- I guess another way to do it is to raise an Exception and return a
single value; although that's not necessarily much easier to read, and it's not
clear what Exception should be raised.

-  if not master_map:
+  if not builders_map:
     return None, 'Failed to build master map.'
 
-  result_master = ''
+  master_map = {}
   for bot in bot_list:
     builder = bot.split(':', 1)[0]
-    master_list = master_map.get(builder, [])
+    master_list = builders_map.get(builder, [])
     if not master_list:
       return None, ('No matching master for builder %s.' % builder)
     elif len(master_list) > 1:
-      return None, ('The builder name %s exists in multiple masters %s.' %
+      return None, ('The builder name %s exists in multiple  masters %s.' %
                     (builder, master_list))
     else:
-      cur_master = master_list[0]
-      if not result_master:
-        result_master = cur_master
-      elif result_master != cur_master:
-        return None, 'The builders do not belong to the same master.'
-  return result_master, None
+      master = master_list[0]
+      master_map.setdefault(master, [])
+      master_map[master].append(bot)
+
+  return master_map, None
 
 
 def CMDtree(parser, args):
@@ -4807,13 +4806,6 @@ def CMDtry(parser, args):
   if options.bucket and options.master:
     parser.error('Only one of --bucket and --master may be used.')
 
-  if options.bot and not options.master and not options.bucket:
-    options.master, err_msg = GetBuilderMaster(options.bot)
-    if err_msg:
-      parser.error('Tryserver master cannot be found because: %s\n'
-                   'Please manually specify the tryserver master'
-                   ', e.g. "-m tryserver.chromium.linux".' % err_msg)
-
   def GetMasterMap():
     # Process --bot.
     if not options.bot:
@@ -4870,7 +4862,16 @@ def CMDtry(parser, args):
       bucket = _prefix_master(options.master)
     return {bucket: builders_and_tests}
 
-  if options.bucket:
+  if options.bot and not options.master and not options.bucket:
+    masters, err_msg = GetBuilderMasters(options.bot)
+    if err_msg:
+      parser.error('Try server masters cannot be found because: %s\n'
+                   'Please manually specify the try server masters'
+                   ', e.g. "-m tryserver.chromium.linux".' % err_msg)
+    buckets = {}
+    for master, builders in masters.iteritems():
+      buckets[_prefix_master(master)] = {b: [] for b in builders}
+  elif options.bucket:
     buckets = {options.bucket: {b: [] for b in options.bot}}
   else:
     buckets = GetMasterMap()