Makes GetBuildTime behave identically on all build types.

build/write_build_date_header.py

Index: build/write_build_date_header.py
diff --git a/build/write_build_date_header.py b/build/write_build_date_header.py
new file mode 100755
index 0000000000000000000000000000000000000000..9ad8eaafa55625166b72e01b0c137bb7f608cc8b
--- /dev/null
+++ b/build/write_build_date_header.py
@@ -0,0 +1,38 @@
+#!/usr/bin/env python
+# Copyright (c) 2016 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.
+
+# Writes a file that contains a define that approximates the build date.

[M-A Ruel, 2016/02/01 17:52:28]

Convert to docstring.

[Zachary Forman, 2016/02/02 06:30:38]

Done!

+# argv[1] is the location to write the file.
+# If argv[2] == "--official", returns the current date in UTC.
+# Otherwise, returns the first day of the current month (in UTC).
+# If argv[2] == "--override", use argv[3] as the build date.
+
+import sys
+from datetime import datetime
+

[M-A Ruel, 2016/02/01 17:52:28]

2 lines between file level symbols.

[Zachary Forman, 2016/02/02 06:30:38]

Done!

+def BuildDate(build_type):
+  if build_type == "--official":

[M-A Ruel, 2016/02/01 17:52:28]

use single quotes everywhere.

[Zachary Forman, 2016/02/02 06:30:38]

Done!

+    format = "{:%b %d %Y}"
+  else:
+    format = "{:%b 01 %Y}"

[M-A Ruel, 2016/02/01 17:52:28]

I thought about it more and I'd want a slightly more complex algorithm.

I'd want it to switch on Saturday, so that the cold cache rush (first of the
month) never happens during a week day.

To do so, you'll have to change the algorithm to look at the current month, and
if it's between Sunday and Saturday and on the first week of the month, it
should return the month before. Does it makes sense?

[Zachary Forman, 2016/02/02 06:30:38]

I like this idea. I'd want it to switch on Sunday in GMT, so that it hits the US
(at 8 hours behind) on a Saturday afternoon instead of a Friday afternoon, and
Australia (on the other end) relatively early on a Sunday morning.

+  return format.format(datetime.utcnow())
+
+def main(arguments):
+  output_location = arguments[1];

[M-A Ruel, 2016/02/01 17:52:28]

No trailing ;

[Zachary Forman, 2016/02/02 06:30:38]

Done

+  build_type = arguments[2] if len(arguments) > 2 else "default"

[M-A Ruel, 2016/02/01 17:52:28]

Please use argparse. It's going to make the script almost 2x longer but it
removes the risk of a parsing error.

[Zachary Forman, 2016/02/02 06:30:38]

Done!

+  if len(arguments) > 2 and arguments[2] == "--override":
+    build_date = arguments[3]
+  else:
+    build_date = BuildDate(build_type)
+  with open(output_location, "w") as output_file:
+    output_file.write("// Generated by //build/write_build_date_header.py\n")
+    output_file.write("#ifndef BUILD_DATE\n")
+    output_file.write("#define BUILD_DATE \"{}\"\n".format(build_date))
+    output_file.write("#endif // BUILD_DATE\n")
+  return 0
+
+
+if __name__ == '__main__':
+  sys.exit(main(sys.argv))