TableOfContents

Developing with DVCS

Distributed Version Control Systems are a huge improvement in the system development process for a number of reasons but its easily researched on Google. So, I'm not going to get into to all the issues. Some thoughts

1. There are only branches and revisions.
   • Think of code development as a process through time and space.
   • Space is discretized into developers
   • Time is discretized into commits
   • Add a little meta data linking points in the developer / commit sequence and you have a graph describing the evolution of the code. Throw on some collision free identifiers (SHA-1) and you have the complete genetic history of every line of code
   • Repositories are a cache / detail without significance in and of themselves
   • don't forget to push often so others can import your changes
2. Only push to repos you own

   • This is probably the least understood aspect of DVCS. The key concept to understand here is that as long as you can get other people's work, you should be pulling and merging from their repos, and only pushing to your own. An example is the repo on your laptop being pushed to your repo on the server for publishing.

   • When your repo is published, others can pull / merge / publish. By convention, cerain people's repos, specfically, certain branches on well known repos will have meaning.
   • There are no permissions required which turns version control on its head. You publish your work, make it known (the usual suspects), and it can be pulled by anyone with interest and as part of the process used by a specific project

3. You are not your code - http://blog.red-bean.com/sussman/?p=96

4. Relevant Videos - on Git but the concepts are explained

   • http://video.google.com/videoplay?docid=-2199332044603874737&q=&hl=en

   • http://video.google.com/videoplay?docid=-3999952944619245780

Hg for sage-finance and dsageng

The suggestion is to to publish your Hg repo's. For most, this will mean pushing to a repo in your home directory on sage.math. I'll pull revisions / branches into my repo which is, by convention only, the official state for finance and dsageng.

1. It is critical to push to your public repo often. We'll come up with a naming convention but there will be branches marked as your current working state. You shouldn't merge your working branch into your "ready to merge with ghtdak branch" unless you've checked for collisions with the blessed trunk at a minimum... and it would help if you would check for collisions with my primary working branch.
2. When a feature is ready for review, an aggregate patch should be assembled and posted on trac consistent with the Sage review process

To facilitate this process, my Hg repo, can be found at

http://tarbox.org:9000 which can be browsed and "pulled" from using hg....

I'll also clone my repo on sage.math from time to time but thats really only useful for those with accounts on that machine and as a backup / disaster mechanism... of course, as we'll be replicating all the changes amongst ourselves, the implied backup strategy of distributed development is very useful.

You should read the mercurial docs... but some hints.

If you want a clean all by itself repo with all the history from the beginning of time:

hg clone http://tarbox.org:9000 sage-ght

remember about branches. Some helpful commands

• hg help branches
• hg help branch
• hg help clone
• hg update -C finpatch
• figure out how to get hg view to work
  • hint: get hgk from the mercurial site, adjust your .hgrc
  • this will likely be part of the sage distro soon enough.
• hg view is nice but doesn't show branch names... I don't get it... but, fortunately, there's hg glog which makes a pretty nice ascii graph which includes branch info. You need to enable the extension... all documented.

ghtdak repo

I develop using Git and the commits there are much more frequent.

My Git repo: http://tarbox.org:8080

CategoryDevelopment