Re: [Monotone-devel] a little status update

[Nathaniel Smith]

On Mon, Dec 06, 2004 at 05:23:14AM -0800, Nathaniel Smith wrote:
> We need to examine this more carefully; I might even be mistaken about
> it.  But in the mean time, my suggestion would be:
>   -- commit to net.venge.monotone if you can
>   -- if not, commit to net.venge.monotone.changesets, after updating
>      to either ae39 (graydon's head) or 094b (my head)
>   -- in no case merge the heads of net.venge.monotone.changesets, that
>      just creates a new head that's even harder to merge.
>   -- don't do any big merges until we have a better idea what was
>      going on with the extremely broken data I think I saw Monotone
>      generate when trying to propagate from .changesets...

Update, based on a little more testing (but still not completely
analyzed, and neither graydon nor I has time to look at it any more
right this second):

There does appear to be some sort of serious bug in the merge
algorithm (or at least propagate).  This is true of _all_ current
heads -- everything on net.venge.monotone and
net.venge.monotone.changesets is, as far as we know, susceptible.

Merging does seem to work fine in most cases, and we have reason to
think that this has already happened; the only case that's known to
trigger it is if you attempt right now doing:
  $ monotone --branch=net.venge.monotone.changesets merge
  $ monotone propagate net.venge.monotone.changesets net.venge.monotone
(how you actually resolve the many conflicts doesn't matter)
You end up with a revision like
  http://frances.vorpus.org/~njs/5933b9d69d08b4cc8525c0c8aa476be583d66ae9
where the add_file stuff is complete nonsense.
I noticed the wierdness before pushing the merge, so it never escaped
into the official database.

We don't know what's causing the bug yet, so we can't say yet how to
detect whether it has previously occurred, or what conditions might
trigger it in the future.  So you might want to hold off on doing
merging for a few days until we've figured out what's going on.

Now that I've gotten everyone nice and scared :-) -- it's probably not
that bad; the worst case scenario is that 0.16 would have to have
another 0.15-style migration, that might lose rename information and
some trust information.  But any garbage data is all in Monotone's
internal bookkeeping structures (and not the most critical parts of
those, either); your data is still safe.

-- Nathaniel

-- 
- Don't let your informants burn anything.
- Don't grow old.
- Be good grad students.
  -- advice of Murray B. Emeneau on the occasion of his 100th birthday