I wish that a command (possibly just "darcs optimize --reorder") would sort the
patches into some consistent order, such that if I run that command one one
repository, and I run that command on another repository which has exactly the
same set of patches in it, then afterward the two repositories will have exactly
the same order.

This is useful for trac, which assigns a sequence number to each patch, e.g.
http://allmydata.org/trac/darcs-2 , and for the versioning scheme that we use
for allmydata.org "Tahoe" project, where the intermediate releases are numbered
by how many patches were in them since the most recent tag:

http://allmydata.org/source/tahoe/tarballs/

It would also be useful for a new versioning scheme that I am thinking of adding
to Tahoe -- take the hash of the output of the "darcs changes --context" and
include that in the version number, so that if you see two versions with the
same hash code then you know that the two were built from the same version of
the source.

Finally, this consistent sort order could be useful for two programmers who are
"comparing" notes and reading through their changes.

Zooko,

It's reasonable idea. It seems work discussing on the mailing list to gather
more feedback.

Would this allow you to 'obliterate' a patch that is being tracked with 'Trac'.
I can't see that it would. Perhaps that's a seperate issue, and one that could
be solved on the Trac side.

Hey Mark Stosberg -- welcome back!  :-)

Unfortunately, I don't think optimize --redorder  will do what you want.  

I believe this would just be an extension of the work needed for minimal
contexts so I'm marking this deferred until we get there.

I suppose this could then work its way into the reorder code so that patches
also get reordered according to scheme.