Fix git cl upload deadlock.

third_party/upload.py

 #!/usr/bin/env python
 # coding: utf-8
 #
 # Copyright 2007 Google Inc.
 #
 # Licensed under the Apache License, Version 2.0 (the "License");
 # you may not use this file except in compliance with the License.
 # You may obtain a copy of the License at
 #
 #     http://www.apache.org/licenses/LICENSE-2.0
@@ skipping 845 matching lines @@
   Returns:
     Tuple (stdout, stderr, return code)
   """
   LOGGER.info("Running %s", command)
   env = env.copy()
   env['LC_MESSAGES'] = 'C'
   p = subprocess.Popen(command, stdout=subprocess.PIPE, stderr=subprocess.PIPE,
                        shell=use_shell, universal_newlines=universal_newlines,
                        env=env)
   if print_output:
+    # It's very hard to stream both stdout and stderr at the same time
+    # without the potential for deadlocks. We will hope for the best

[tandrii(chromium), 2015/12/22 14:49:37]

indeed, hard. we have a subprocess2 module for this purpose:

https://chromium.googlesource.com/chromium/tools/depot_tools/+/master/subproc...
, but after looking into it, i don't see immediate replacement.

+    # since this code path is rarely used.
     output_array = []
     while True:
       line = p.stdout.readline()
       if not line:
         break
       print line.strip("\n")
       output_array.append(line)
     output = "".join(output_array)
+    p.wait()
+    errout = p.stderr.read()
+    if errout:
+      print >> sys.stderr, errout
   else:
-    output = p.stdout.read()
-  p.wait()
-  errout = p.stderr.read()
-  if print_output and errout:
-    print >> sys.stderr, errout
+    output, errout = p.communicate()
   p.stdout.close()
   p.stderr.close()
   return output, errout, p.returncode
 
 def RunShellWithReturnCode(command, print_output=False,
                            universal_newlines=True,
                            env=os.environ):
   """Run a command and return output from stdout and the return code."""
   out, err, retcode = RunShellWithReturnCodeAndStderr(command, print_output,
                            universal_newlines, env)
@@ skipping 551 matching lines @@
         extra_args = self.options.revision.split(":", 1) + extra_args
       else:
         extra_args = [self.options.revision] + extra_args
 
     # --no-ext-diff is broken in some versions of Git, so try to work around
     # this by overriding the environment (but there is still a problem if the
     # git config key "diff.external" is used).
     env = os.environ.copy()
     if "GIT_EXTERNAL_DIFF" in env:
       del env["GIT_EXTERNAL_DIFF"]
+    # 'cat' is a magical git string that disables pagers on all platforms.
+    env["GIT_PAGER"] = "cat"
+
     # -M/-C will not print the diff for the deleted file when a file is renamed.
     # This is confusing because the original file will not be shown on the
     # review when a file is renamed. So, get a diff with ONLY deletes, then
     # append a diff (with rename detection), without deletes.
     cmd = [
         "git", "diff", "--no-color", "--no-ext-diff", "--full-index",
         "--ignore-submodules", "--src-prefix=a/", "--dst-prefix=b/",
     ]
     diff = RunShell(
         cmd + ["--no-renames", "--diff-filter=D"] + extra_args,
@@ skipping 1088 matching lines @@
     print
     StatusUpdate("Interrupted.")
     sys.exit(1)
   except auth.AuthenticationError as e:
     print >> sys.stderr, e
     sys.exit(1)
 
 
 if __name__ == "__main__":
   main()