2.0.0 migration report: darcs

Hi,

The darcs project recently migrated from an instance of roundup 1.4.15
running on an ancient server to roundup 2.0.0. At John Rouillard's
suggestion, I'm sending a brief summary of our migration experience.

We have about 500-1000 users (most currently inactive, and many are
spammers anyway), 3000 issues and 2000 patches which we track separately
in roundup.

Overall I was quite happy about smoothly the process went compared to my
initial concerns about how painful such a big jump could have been. It
was also greatly assisted by various help and support from John
Rouillard on IRC.

I decided to keep things as simple as possible in the new setup so
moved from postgresql to sqlite.

There were a couple of gotchas with the export/import procedure.
Firstly, the export produced some literals like '850L' which stopped
being supported in python3. As a result I decided to start by migrating
to python2 on the new server, and then consider doing an upgrade later.

Secondly our instance has a number of "retired" users and I ran into a
bug in the import procedure relating to when the relevant flag is set.
John Rouillard was very quick to diagnose the problem and suggest
immediate workarounds. I ended up using a script to reorder the user
records to avoid the bug.

The other main migration task was merging our config.ini and schema.py
files with the latest defaults in 2.0.0, and likewise with our detectors
and incoming mail handling. I ended up figuring out the last two items
on our live instance post-migration because it wasn't worth the effort
to set up full mail handling for the testing instance first, but this
didn't prove to be a major problem.

Cheers,

Ganesh