Show the current SVN revision in your Rails app

I’m current developing a Rails application. I deploy this application to a demonstration server using capistrano.

To streamline feedback and bug reporting I want to show the current revision number of the code that’s published on the demo server to show in the footer of every page.

First I looked into Subversion keyword expansion, but this is marked as ‘evil’ and it doesn’t meet my requirements. I want to show the latest revision number of the entire repository and not just that of the current file.

Luckily for me, I use capistrano. Here’s how I fixed the problem.

First of all, I created a partial that contains the revision number and render this in my layout.

app/views/layouts/_revision.rhtml:

CURRENT

This shows CURRENT always when I work with my working copy.

app/views/layouts/mylayout.rhtml

  < %= render :partial => 'layout/revision' %>

Now, I assume you have already setup capistrano for your project and that you have a config/deploy.rb file.

I’ve added the following helper to my config/deploy.rb file:

desc "Write current revision to app/layouts/_revision.rhtml"
task :publish_revision do
  run "svn info #{release_path} | grep ^Revision > #{release_path}/app/views/layouts/_revision.rhtml"
end

Next, I added the following hook ‘after_update_code’. This will automatically be run after update_code which is called in ‘deploy’.

desc "Run this after update_code"
task :after_update_code do
  publish_revision
end

That’s it. When I deploy the application, the current code is checked out and and the layouts/_revision.rhtml file is overwritten with the current revision information.

Bonus

You could also leave the layouts/_revision.rhtml files empty and update it for your demonstration server, but not for your production box. This way there won’t be a revision added.

Of course, you could also create a deploy_demonstration method in deploy.rb and call publish_revision manually from there.

Tags: Capistrano, Everything, RubyOnRails, Subversion

This entry was posted on Wednesday, December 13th, 2006 at 13:38 and is filed under Features, General. You can follow any responses to this entry through the RSS 2.0 feed. You can leave a response, or trackback from your own site.

9 Responses to “Show the current SVN revision in your Rails app”

Bitbutter says:
28 January, 2007 at 15:04
Thanks for this write-up! i was thinking about the best way to do this very thing.
Aaron Namba says:
16 March, 2007 at 03:55
That seems… complicated. I use svnversion to get that info. It’s a bit slow though, so I cache the result. This is from my application.rb:
def build_number
if RAILS_ENV == ‘production’
if !defined?(@@build_number)
svnversion = `svnversion #{RAILS_ROOT}`
svnversion =~ /:?(\d )[MS]?$/
@@build_number = $1
end
@@build_number
else
‘BUILD’
end
end
helper_method :build_number
Ariejan says:
16 March, 2007 at 11:15
Your version has to run subversion every time you request the active revision.
My script only does that once so there would be a performance advantage to my version.
Alexander says:
13 April, 2007 at 18:23
Hi,
since ’svn info’ output is pretty much YAML, I simply do the following:
deploy.rb:
task :publish_revision do
run “svn info #{release_path} > #{release_path}/config/appversion.yml”
and then in the app: read this file as a hash:
environment.rb:
APP_VERSION = File.file?(‘config/appversion.yml’) ? YAML.load_file(‘config/appversion.yml’) : “”
in the view:
< %= APP_VERSION %>
and so on :)
jc says:
18 June, 2007 at 05:40
Capistrano now seems to give you a “revision” variable for free.
This is what I’m doing:
run “echo \”REVISION:#{revision}\” > #{release_path}/app/views/shared/_version.rhtml”
de tomKronieken » Blog Archive » links for 2008-01-09 says:
9 January, 2008 at 20:21
[...] Ariejan.net » Show the current SVN revision in your Rails app Shared with shareomatic.com (tags: rails svn) [...]
Elwyn says:
16 May, 2008 at 15:53
Great article and comments, really helpful. However, what you actually need is the following if your using capistrano’s “free” revision number.
run “echo \”REVISION:#{real_revision}\” > #{release_path}/app/views/shared/_version.rhtml”
revision will just spit out a useless “HEAD”
:-)
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23 February, 2009 at 13:00
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Marcin Kulik says:
1 June, 2009 at 00:21
Guys, try my Rack middleware for showing revision info on demo/staging servers. It allows to completely remove revision-displaying code from your app’s layout and/or partials (which shouldn’t be there at all). Check it out at http://sickill.net/blog/2009/06/01/rack-middleware-showing-git-or-svn-revision.html

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