phases: apply similar early filtering to advanceboundary
advanceboundary is called the push's unbundle (but not the other unbundle) so
advanceboundary did not show up the profile I looked at so far.
We start with simple pre-filtering to avoid doing any work if we don't needs
too.
import sys
for line in sys.stdin:
if line.lower() in ("message-id: \n", "in-reply-to: \n"):
line = line[:-2]
print(line, end="")