Difference between step output

[ranma42]

The possibility to compare the logs of a build with the corresponding ones of the previous build is often very useful to make it more obvious what are the changes (new/fixed warnings, failures, etc).

How hard would it be to implement such a feature?

I know some Python, but I don't know much about Buildbot, so I would need some help to get started (currently I'm doing something like this in a hack-like MasterShellCommand? step which calls into an external script).

[dustin]

Comparing the state isn't too hard - you could probably do so from a status plugin that's similar to the MailNotifier?.

What's tricky is to define "previous build" - is that ordered by time, or by commit history? If you're using a non-monotonic version control system (e.g., git with unordered sha1's), how do you determine "previous"? Even with svn, if you have a build for r10010 and r10012, do you wait for a potential r10011 to arrive before comparing? What about parallel builds where r10012 is on a faster slave and finishes before r10010? What if two builds by a particular builder are for different branches? If you take that into account, what happens if the previous build on a branch has been purged from the status history?

If all of these questions have simple answers for your install of Buildbot, then this should be fairly straightforward for you. For the reasons outlined above, such a thing is unlikely to be included in Buildbot itself (although I would be happy to see a reference to it somewhere on the wiki!)