git cl split: Don't cq dry run by default

`git cl split` currently runs a cq dry run for every uploaded CL. This
has overloaded our infrastructure a few times in the past. This CL changes
the command to not dry run by default, and adds a flag to enable this. The
flag has a warning about doing this, and tells the user to email
infra-dev@chromium.org if they're going to be generating >~10 CLs.

Bug: 878117
Change-Id: Ic865c09b188b8d4f202785f4763f7b7b8910c9cf
Reviewed-on: https://chromium-review.googlesource.com/1191927Reviewed-by: Andrii Shyshkalov <tandrii@chromium.org>
Reviewed-by: Edward Lesmes <ehmaldonado@chromium.org>
Commit-Queue: Stephen Martinis <martiniss@chromium.org>

git_cl.py

@@ -5142,6 +5142,13 @@ def CMDsplit(parser, args):
                     default=False,
                     help="List the files and reviewers for each CL that would "
                          "be created, but don't create branches or CLs.")
+  parser.add_option("--cq-dry-run", action='store_true',
+                    help="If set, will do a cq dry run for each uploaded CL. "
+                         "Please be careful when doing this; more than ~10 CLs "
+                         "has the potential to overload our build "
+                         "infrastructure. Try to upload these not during high "
+                         "load times (usually 11-3 Mountain View time). Email "
+                         "infra-dev@chromium.org with any questions.")
   options, _ = parser.parse_args(args)
 
   if not options.description_file:
@@ -5151,7 +5158,8 @@ def CMDsplit(parser, args):
     return CMDupload(OptionParser(), args)
 
   return split_cl.SplitCl(options.description_file, options.comment_file,
-                          Changelist, WrappedCMDupload, options.dry_run)
+                          Changelist, WrappedCMDupload, options.dry_run,
+                          options.cq_dry_run)
 
 
 @subcommand.usage('DEPRECATED')

split_cl.py

@@ -67,7 +67,8 @@ def AddUploadedByGitClSplitToDescription(description):
 
 
 def UploadCl(refactor_branch, refactor_branch_upstream, directory, files,
-             description, comment, reviewers, changelist, cmd_upload):
+             description, comment, reviewers, changelist, cmd_upload,
+             cq_dry_run):
   """Uploads a CL with all changes to |files| in |refactor_branch|.
 
   Args:
@@ -81,6 +82,7 @@ def UploadCl(refactor_branch, refactor_branch_upstream, directory, files,
     reviewers: A set of reviewers for the CL.
     changelist: The Changelist class.
     cmd_upload: The function associated with the git cl upload command.
+    cq_dry_run: If CL uploads should also do a cq dry run.
   """
   # Create a branch.
   if not CreateBranchForDirectory(
@@ -107,7 +109,9 @@ def UploadCl(refactor_branch, refactor_branch_upstream, directory, files,
     os.remove(tmp_file.name)
 
   # Upload a CL.
-  upload_args = ['-f', '--cq-dry-run', '-r', ','.join(reviewers)]
+  upload_args = ['-f', '-r', ','.join(reviewers)]
+  if cq_dry_run:
+    upload_args.append('--cq-dry-run')
   if not comment:
     upload_args.append('--send-mail')
   print 'Uploading CL for ' + directory + '.'
@@ -156,7 +160,8 @@ def PrintClInfo(cl_index, num_cls, directory, file_paths, description,
   print
 
 
-def SplitCl(description_file, comment_file, changelist, cmd_upload, dry_run):
+def SplitCl(description_file, comment_file, changelist, cmd_upload, dry_run,
+            cq_dry_run):
   """"Splits a branch into smaller branches and uploads CLs.
 
   Args:
@@ -165,6 +170,7 @@ def SplitCl(description_file, comment_file, changelist, cmd_upload, dry_run):
     changelist: The Changelist class.
     cmd_upload: The function associated with the git cl upload command.
     dry_run: Whether this is a dry run (no branches or CLs created).
+    cq_dry_run: If CL uploads should also do a cq dry run.
 
   Returns:
     0 in case of success. 1 in case of error.
@@ -198,6 +204,16 @@ def SplitCl(description_file, comment_file, changelist, cmd_upload, dry_run):
     num_cls = len(files_split_by_owners)
     print('Will split current branch (' + refactor_branch + ') into ' +
           str(num_cls) + ' CLs.\n')
+    if cq_dry_ru and num_cls > CL_SPLIT_FORCE_LIMIT:
+      print (
+        'This will generate "%r" CLs. This many CLs can potentially generate'
+        ' too much load on the build infrastructure. Please email'
+        ' infra-dev@chromium.org to ensure that this won\'t  break anything.'
+        ' The infra team reserves the right to cancel your jobs if they are'
+        ' overloading the CQ.') % num_cls
+      answer = raw_input('Proceed? (y/n):')
+      if answer.lower() != 'y':
+        return 0
 
     for cl_index, (directory, files) in \
         enumerate(files_split_by_owners.iteritems(), 1):
@@ -212,7 +228,8 @@ def SplitCl(description_file, comment_file, changelist, cmd_upload, dry_run):
                     reviewers)
       else:
         UploadCl(refactor_branch, refactor_branch_upstream, directory, files,
-                 description, comment, reviewers, changelist, cmd_upload)
+                 description, comment, reviewers, changelist, cmd_upload,
+                 cq_dry_run)
 
     # Go back to the original branch.
     git.run('checkout', refactor_branch)