view mercurial/node.py @ 24305:867c3649be5d

cvsps: use a different tiebreaker to avoid flaky test

After adding some sneaky debug printing[0], I determined that this
test flaked when a CVS commit containing two files starts too close to
the end of a second, thus putting file "a" in one second and "b/c" in
the following second. The secondary sort key meant that these changes
sorted in a different order when the timestamps were different than
they did when they matched. As far as I can tell, CVS walks through
the files in a stable order, so by sorting on the filenames in cvsps
we'll get stable output. It's fine for us to switch from sorting on
the branchpoint as a secondary key because this was already the point
when we didn't care, and we're just trying to break ties in a stable
way. It's unclear to be if having the branchpoint present matters
anymore, but it doesn't really hurt to leave it.

With this change in place, I was able to run test-convert-cvs over 650
times in a row without a failure.  test-convert-cvcs-synthetic.t
appears to still be flaky, but I don't think it's *worse* than it was
before - just not better (I observed one flaky failure in 200 runs on
that test).

0: The helpful debug hack ended up being this, in case it's useful to
future flaky test assassins:

 --- a/hgext/convert/cvsps.py
 +++ b/hgext/convert/cvsps.py
 @@ -854,6 +854,8 @@ def debugcvsps(ui, *args, **opts):
              ui.write(('Branch: %s\n' % (cs.branch or 'HEAD')))
              ui.write(('Tag%s: %s \n' % (['', 's'][len(cs.tags) > 1],
                                    ','.join(cs.tags) or '(none)')))
 +            if cs.comment == 'ci1' and (cs.id == 6) == bool(cs.branchpoints):
 +                ui.write('raw timestamp %r\n' % (cs.date,))
              if cs.branchpoints:
                  ui.write(('Branchpoints: %s \n') %
                           ', '.join(sorted(cs.branchpoints)))

# node.py - basic nodeid manipulation for mercurial
#
# Copyright 2005, 2006 Matt Mackall <[e-mail]>
#
# This software may be used and distributed according to the terms of the
# GNU General Public License version 2 or any later version.

import binascii

nullrev = -1
nullid = "\0" * 20

# This ugly style has a noticeable effect in manifest parsing
hex = binascii.hexlify
bin = binascii.unhexlify

def short(node):
    return hex(node[:6])