Adds saner behavior for git try -t foo to not fail in a inexplicable way. Enforces that each builde…

trychange.py

Index: trychange.py
diff --git a/trychange.py b/trychange.py
index 748dbfa6cd45f90c68ab69fcc255f238645fe3e3..e37347c677fc8b978b0780cfc6fa529b195a2002 100755
--- a/trychange.py
+++ b/trychange.py
@@ -805,6 +805,16 @@ def TryChange(argv,
             sys.stdout)
       except ImportError:
         pass
+      if options.testfilter:
+        bots = set()
+        for bot in options.bot:
+          assert ',' not in bot
+          if bot.endswith(':compile'):
+            # Skip over compile-only builders for now.
+            continue
+          bots.add(bot.split(':', 1)[0])
+        options.bot = list(bots)
+
       # If no bot is specified, either the default pool will be selected or the
       # try server will refuse the job. Either case we don't need to interfere.