CI and the Change Log
Does continuous integration mean you can't have a clean change log? This developer says no — keep reading to find out how.
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I get into debates about the relative merits of "Continuous Integration (and Delivery)" vs those of "Feature Branching" on a fairly regular basis. A common push-back against CI, from the feature-branchers, is "you can't maintain a clean change-log." I guess this depends on how important you think the change-log is and what it is for. Is the change-log equally, or more important than working software? Of course not!
I know that statement is a bit extreme but it is kind of a relevant question. CI is a practice that comes with some trade-offs, but it is the best way that we have discovered of maintaining our software in a working state so far.
An analysis from the "2017 State of DevOps Report" found the following:
"High performers have the shortest integration times and branchlifetimes, with branch life and integration typically lasting hours.Low performers have the longest integration times and branch lifetimes, with branch life and integration typically lasting days.These differences are statistically significant."
The VCS change log tells a story, but what is the story and what is it for? If I connect my "story/requirements management system" (JIRA, etc) to my VCS via a tag in the commit message, I can trace every commit to a story. So I have traceability. So I guess the next question is what are the use-cases for a change-log?
I can think of two broad groups of uses for a change-log:
Some kind of audit-trail of changes, maybe useful for a regulator or compliance person to see the history of changes.
An index of changes that a developer can use to navigate the history.
If I adopt CI, and make fine-grained, regular commits, each of them commented on and linked to a story (or bug), then I can tell the story of the story. I have my audit trail. It will be very detailed. It may even wander around a bit "Make the button blue" and later "Make the button green" but that was the true story of the development. This is a good, accurate representation of the life of the change.
I know that each commit was related to the story, so from the perspective of an auditor, I have a definitive, albeit granular, statement.
From the perspective of a developer wanting to know what change did what, I have a more detailed picture that too, because of this more granular reporting. I can build up the story, in fine detail of the evolution of the ideas. I have not lost anything, I have more information not less. The picture may be a bit messier, but that only represents the reality of the evolution of the design.
I confess that I don't really understand the desire for a "clean change log." What does that mean? It seems to me to imply an assumption that once I have finished a "Story" I am done.
What is the difference between me playing "Story 1", which "makes the Button green" and later "Story 5" which "makes the button blue" and me changing my mind in the midst of "Story 3" and making the same change?
I think that this desire for a "clean change-log" may be based on an illusion of software development as an ever-increasing collection of desirable features rather than as an exploration of a problem-space. I think that development is much messier than that. It is much more the latter than the former. If we are not learning-as-we-go that some of our ideas are wrong, we are not doing a very good job of software development. In my world, however granular or not, the idea of a "clean change-log" is an illusion.
I don't believe that software development is like that. However I work, I am going to be returning to the code over and over again and refining and updating it as requirements are added and as my understanding evolves. So even if I have a log entry per commit, I still need to read them all to know the state of the system at any given point, the only difference is one of granularity.
I am increasingly starting to view the collection of a fine-grained picture of the changes in our development process as an asset, not as a liability. Instead of thinking of the change-log as a linear record, think of it as part of the "historical search-space" of information, linked by keys (like the id of your story and the id of your release candidates), that you can navigate to build any picture you like of what happened. To my mind, that is a more powerful tool, not a less powerful one.
Published at DZone with permission of Dave Farley, DZone MVB. See the original article here.
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