Managing dependencies
using Piston
David Peterson
peterson@orbitec.com.au

Plugins
Most rails applications make
use of one or more plugins.
These are typically versioned using
subversion.

svn:externals
Plugins are conventionally imported
●
into a rails application as external
repositories
$ svn co
http://elitists.textdriven.com/svn/plu
gins/acts_as_state_machine/trunk/
acts_as_state_machine

Problems with this approach
What if the remote repository is down
●
when you want to:
Do a fresh checkout
●
DEPLOY ?!
●
What if you want to version your local
●
changes to the plugin?
What if you want to sync your changes
●
with upstream updates?

One answer ...
Use Piston
for dependency
management
http://piston.rubyforge.org/

Piston
'Easy vendor branch management'
●
Moves from using svn:externals to
●
using conventional (svn) directories
Piston manages synchronisation with
●
upstream repository
Best of both worlds
●

Getting started ...
$ (sudo) gem install piston ­y
$ cd myapp/vendor/plugins
$ piston convert
$ svn commit
$ piston import http://...

Features
Hack local plugin with abandon :)
●
$ piston import http://...
Lock deps to a specific version
●
$ piston lock vendor/rails
Merge updates at any time (if !locked)
●
$ piston update

Example
$ cd myapp/vendor/plugins
$ piston st
attachment_fu
(http://svn.techno­
weenie.net/projects/plugins/attachment
_fu)
M acts_as_state_machine
(http://elitists.textdriven.com/svn/pl
ugins/acts_as_state_machine/trunk)
...