| Re: [orion-dev] a story about "checkout by tag" and finding regressions |
For those who don't know, Gosia/Tomek added "checkout by tag" support in RC3. [1]
And for those who don't know, I have vowed to be a loyal self hoster, and to never leave orion.eclipse.org for the command line, which means that sometimes I have to do stupid things to get my work done, in the name of discovering holes in our code. And so far, even the stupidest workarounds haven't cost me too badly.
Anyway...here is a cool, albeit manual, scenario that I was able to do today because of the "checkout by tag" support.
- I noticed a regression in the code [2]
- I wasn't sure where the code change had occurred, though I had suspicions, and I was pretty sure I had caused it.
- I wanted to "git bisect" so that I could find exactly where the behavior broke. But we don't have that yet, so...
- I looked at the list of tags for the org.eclipse.orion.client.core repository and checked out the first build since I returned from summer break.
- I always have a self hosting site running, so I refreshed the page in that site to confirm that the code was working properly
- I visually "bisected" by checking out by tag a build halfway between today and that day in the branch list, reloaded the page, tested
- continued bisecting and retesting until I found where it broke
- it only took about 5 minutes to find the breakage, most of that being reloading and testing the behavior (which you have to do regardless of how you go about bisecting)
- having found the two builds, one good, the next bad, I just put a breakpoint in my code on the self hosting site, and then could see a good parameter coming in, and then a bad one. So I knew where things had gone wrong
- At that point, I used git log to look at the commits in the two branches, and from there I knew which change it was and quickly found it. I suppose I could have rebased one branch on the other in order to look at diffs (vs. git log), but since I was familiar with the code I knew exactly which commit and file was causing the problem.
Cool!
susan
[1] https://bugs.eclipse.org/bugs/show_bug.cgi?id=360193
[2] https://bugs.eclipse.org/bugs/show_bug.cgi?id=361481
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