The Vienna team had a unique experience as the sprint happened to coincide with a student protest that resulted in an occupied University building. Great fun was had by all as we shared our hacking space with the Occupiers on Saturday.
The Portland team was graciously hosted by Galois. As a special treat, we got a visit from Thomas Hartman, one of the folks behind Patch-tag.
Overview
Among other things, the upcoming Darcs 2.4 release has some nice performance improvements from Petr Ročkai's hashed-storage work.One first goal in this sprint was to polish up this work, making our hashed repository support good enough for GHC team to upgrade from the deprecated old-fashioned format. We think we've largely accomplished what we set out to do. Read on for more details!
Our second goal was to provide a space for new Darcs hackers to get started with making contributions to the project. We had 14 new Darcs developers at this sprint! We hope that they will stay on with the project and continue submitting patches.
Issues resolved
Note that some of this work is still pending patch review or amendements.- issue540 - darcs remove --recursive - Roman Plášil
- issue835 - show files with arguments - Luca Molteni
- issue1122 - get --complete UI - David Markvica
- issue1208 - trackdown --bisect - Matthias Fischmann, Radoslav Dorcik
- issue1224 - darcs convert on darcs-2 repositories - Tomáš Caithaml
- issue1377 - hardcoding of darcs executable name - Benedikt Huber
- issue1392 - use Parsec for authorspellings - Tomáš Caithaml
- issue1394 - show time elapsed after each test - Kim Wallmark
- issue1499 - versioned show files - Thomas Hartman
- issue1500 - misleading darcs progress reports - Roman Plášil
- issue1624 - break up global cache into subdirectories - Luca Molteni
- issue1643 - optimize --upgrade should do optimize - Christian Berrer
Hacking
Studying darcs
Thomas DuBuisson and Jason Dagit studied some hanging merge cases on the GHC repository to see if we could garner some insights into them. While this did not yield much fruit, it did result a few code cleanups.Jonathan Daugherty and Josh Hoyt took a tour of the Darcs source. We hope they'll be joining us as Darcs hackers in the future :-)
Jason Dagit produced a concrete and low-level description of the Darcs record command.
Code cleanups
Tomáš Caithaml simplified the darcs show authors authorspellings code by rewriting it in Parsec.Jason Dagit cleaned up the elegant_merge function and removed commutex in favor of commute.
Jonathan Daugherty submitted some improvements to the user manual.
Performance improvements
User interface improvements
Tomáš Caithaml got darcs convert to abort in case user accidently tries to convert a darcs 2 repository a second time.
OLD TEXT NEW TEXT
Fetching pristine cache... 4/45 4 done, 41 queued
(sometime later)... 10/166 10 done, 155 queued
(finally)... 297/297 297 doneDavid Markvica modified darcs get --complete so that it no longer offers to create a lazy repository.
Benedikt Huber relaxed the assumption that darcs executable would be called "darcs", instead fetching this from the command line.
New features
Roman Plášil implemented an oft-requested remove -r feature, making it easier to undo accidental adds of large directories.
Luca Molteni implemented darcs show files with an argument to limit the output to a specific file or directory.
Thomas Hartman implemented matchers support for darcs show files, allowing to get the list of files tracked by Darcs at a given point in the history (eg. darcs show files --tag 2.4).
Petr Ročkai worked on a new more extensible, self-documenting format mechanism as a future alterantive to _darcs/format.
UTF-8 Support
SVN integration
Zero Windows Bugs!
Darcs Team infrastructure
Kim Wallmark worked on making the 'cabal test' friendlier by outputting the amount of time elapsed after long tests.
Discussions
Priorities for the Sprint
Salvatore Insalaco, Eric Kow, Reinier Lamers, Luca Molteni and Petr Ročkai discussed the key goals for the sprint and also produced a list of the top ProbablyEasy.Type witnesses
Jason Dagit gave a presentation about our type-witnesses, how the type hackery in darcs is implemented, and why it is useful.Patch-tag
Thomas Hartman and the Portland crew discussed patch-tag: how it felt from a user perspective and what the most useful features would be.SVN integration
Petr Ročkai and Eric Kow also discussed the nature of patch/changeset based revision control (like Darcs) and snapshot based revision control (everything else). Petr observed that changeset based version control can be seen as just snapshot based control with a fixed diffing algorithm. To support things like SVN integration, Darcs will need to freeze its diffing algorithm.
Darcs roadmap
Salvatore Insalaco, Eric Kow, Reinier Lamers and all Vienna hackers developed the roadmap for Darcs 2.4 (January 2010) and Darcs 2.5 (July 2010). Using a chalkboard we listed the features we wanted, how desirable they were and what order we should do them in.
Windows support
Salvatore Insalaco, Eric Kow and Reinier Lamers discussed the future of Windows support in Darcs.Official binary: Our first priority will be to get an official binary for Windows downloadable from Darcs.net. The upcoming Darcs release (Darcs 2.4 in January 2010) will the first to provide an official binaries. Currently, we have the resources to provide a binary for Windows only, but in the future the list of platforms may grow.
Refined integration: After the Darcs 2.4 release, we will work on developing a friendly Windows installer for Darcs which includes not just the Darcs binary but (optionally), TortoiseSSH for better ssh support and a tool for sending email via darcs send.
Cygwin support: We will not be able to support Cygwin, but we will work on providing more explicit documentation on what works (mostly everything) and what does not (absolute cygwin paths). We think that the improved Windows installer will provide a sufficiently comfortable Darcs experience for most Cygwin users.
Fun and speculation
Joachim Breitner, Reinier Lamers and Petr Ročkai discussed abstracting over patch types to just maps (eg. directories), sets and lists (eg. files).Better Darcs Hacking Sprints
Every sprint teaches something new for what we hope to be a long tradition of biannual Darcs Hacking events.
Replicating success is one thing; how can we do even better? Mainly we need to improve the experience that new hackers have. We were lucky this year to have many new Haskellers and Darcs developers, but we could have done a better job in helping them to get started.
First, some technical issues: A lot of our new developers lost the better part of Saturday morning setting up the machines to build Darcs and to send patches to the list. In the next sprint, we will be ready with much more precise and detailed setup instructions (developed hastily during this sprint) going all the way to the best default settings for Darcs, configuration files for msmtp (or similar sendmail replacements). It also has been suggested that we provide a virtual machine image for instant Darcs hacking.
Second, our mentoring strategy: We were fairly successful at providing in-depth individual mentoring; however what we could done better was to provide more mass mentoring at the very beginning, to help developers send their first patches. To make this work, we should try starting the next sprint with a group mentoring session with the specific purpose of getting people set up to send their first patches. We should encourage new developers to work in small teams, for example with an extra USB keyboard to facilitate pair programming on a single machine.
Attendees
Vienna
- Joachim Breitner
- Benedikt Huber
- Eric Kow
- Reinier Lamers
- David Markvica
- Petr Rockai
- Radoslav Dorcik
- Salvatore Insalaco
- Matthias Fischmann
- Thomas Danecker
- Christian Berrer
- Luca Molteni
- Roman Plášil
- Tomáš Caithaml
- Pivo
Portland
- Jason Dagit
- Josh Hoyt
- Thomas Hartman
- Thomas DuBuisson
- Kim Wallmark
- Jonathan Daugherty
Thanks!
Many thanks to the local team at TU Vienna and Galois for a wonderful welcome! Thanks to the many generous donors who helped us to subsidise travel to the sprint. Thanks also to Microsoft Austria for sponsoring the sprint with drinks and snacks. Molte grazie to Salvatore Insalaco for a wonderful lunch on Sunday.Finally, thanks to Petr and Luca for the photos, and more generally to everybody who participated in the sprint! It was great to have you and we hope to see you again either on the mailing list or at future sprints.
