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authorDaniel Silverstone <dsilvers@digital-scurf.org>2020-05-11 20:31:38 +0100
committerDaniel Silverstone <dsilvers@digital-scurf.org>2020-05-11 20:31:38 +0100
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Posting about book club
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+[[!meta title="The Lars, Mark, and Daniel Club"]]
+[[!meta author="Daniel Silverstone"]]
+[[!meta date="2020-05-11 20:00:00"]]
+[[!tag draft]]
+
+Today [Lars][], [Mark][], and I discussed Jeremy Kun's [The communicative value
+of using Git well][article] post. While a lot of our discussion was spawned by
+the article, we did go off-piste a little, and I hope that my notes below will
+enlighten you all as to a bit of how we see revision control these days. It
+was remarkably pleasant to read an article where the comments section wasn't a
+cesspool of horror, so if this posting encourages you to go and read the
+article, don't stop when you reach the bottom -- the comments are good and
+useful too.
+
+[Lars]: https://blog.liw.fi/
+[Mark]: https://blog.sirena.org.uk/
+[article]: https://jeremykun.com/2020/01/14/the-communicative-value-of-using-git-well/
+
+***
+
+This was a fairly non-contentious article for us though each of us had points
+we wished to bring up and chat about it turned into a very convivial chat.
+We saw the main thrust of the article as being about using the metadata of
+revision control to communicate intent, process, and decision making. We
+agreed that it must be possible to do so effectively with Mercurial (thus
+deciding that the mention of it was simply a bit of clickbait / red herring)
+and indeed Mark figured that he was doing at least some of this kind of thing
+way back with CVS.
+
+We all discussed how knowing the fundamentals of Git's data model improved our
+ability to work wih the tool. Lars and I mentioned how jarring it has originally
+been to come to Git from revision control systems such as Bazaar (`bzr`) but
+how over time we came to appreciate Git for what it is. For Mark this was less
+painful because he came to Git early enough that there was little more than the
+fundamental data model, without much of the [porcelain][] which now exists.
+
+[porcelain]: https://git-scm.com/book/en/v2/Git-Internals-Plumbing-and-Porcelain
+
+One point which we all, though Mark in particular, felt was worth considering
+was that of distinguishing between published and unpublished changes. The
+article touches on it a little, but one of the benefits of the workflow which
+Jeremy espouses is that of using the revision control system as an integral
+part of the review pipeline. This is perhaps done very well with Git based
+workflows, but can be done with other VCSs.
+
+With respect to the points Jeremy makes regarding making commits which are good
+for reviewing, we had a general agreement that things were good and sensible,
+to a point, but that some things were missed out on. For example, I raised
+that commit messages often need to be more thorough than one-liners, but
+Jeremy's examples (perhaps through expedience for the article?) were all pretty
+trite one-liners which perhaps would have been entirely obvious from the commit
+content. Jeremy makes the point that large changes are hard to review, and
+Lars poined out that [Greg Wilson did research][gwilson] in this area, and at
+least one [article][article200] mentions 200 lines as a maximum size of a
+reviewable segment.
+
+[gwilson]: https://arxiv.org/abs/1407.5648
+[article200]: https://uwescience.github.io/neuroinformatics/2017/10/08/code-review.html
+
+I had a brief warble at this point about how reviewing needs to be able to
+consider the whole of the intended change (i.e. a diff from base to tip) not
+just individual commits, which is also missing from Jeremy's article, but that
+such a review does not need to necessarily be thorough and detailed since the
+commit-by-commit review remains necessary. I use that high level diff as a way
+to get a feel for the full shape of the intended change, a look at the end-game
+if you will, before I read the story of how someone got to it. As an aside at
+this point, I talked about how Jeremy included a 'style fixes' commit in his
+example, but I **loathe** seeing such things and would much rather it was
+either not in the series because it's unrelated to it; or else the style fixes
+were folded into the commits they were related to.
+
+We discussed how style rules, as well as commit-bisectability, and other rules
+which may exist for a codebase, the adherence to which would form part of the
+checks that a code reviewer may perform, are there to be held to when they
+**help** the project, and to be _broken_ when they are in the way of good
+communication between humans.
+
+In this, Lars talked about how revision control histories provide high level
+valuable communication _between developers_. Communication between humans is
+fraught with error and the rules are not always clear on what will work and
+what won't, since this depends on the communicators, the context, etc. However
+whatever communication rules are in place should be followed. We often say
+that it takes two people to communicate information, but when you're writing
+commit messages or arranging your commit history, the second party is often
+nebulous "other" and so the code reviewer fulfils that role to concretise it
+for the purpose of communication.
+
+At this point, I wondered a little about what value there might be (if any) in
+maintaining the metachanges (pull request info, mailing list discussions, etc)
+for historical context of decision making. Mark suggested that this is useful
+for design decisions etc but not for the style/correctness discussions which
+often form a large section of review feedback. Maybe some of the metachange
+tracking is done automatically by the review causing the augmentation of the
+changes (e.g. by comments, or inclusion of design documentation changes) to
+explain _why_ changes are made.
+
+We discussed how the "rebase always vs. rebase never" feeling flip-flopped in
+us for many years until, as an example, what finally won Lars over was that he
+wants the history of the project to tell the story, in the git commits, of how
+the software has changed and evolved in an **intentional** manner. Lars said
+that he doesn't care about the meanderings, but rather about a clear story
+which can be followed and understood.
+
+I described this as the switch from "the revision history is about what I did
+to achieve the goal" to being more "the revision history is how I would hope
+someone else would have done this". Mark further refined that to "The revision
+history of a project tells the story of how the project, as a whole, _chose_ to
+perform its sequence of evolution."
+
+We discussed how project history must necessarily then contain issue tracking,
+mailing list discussions, wikis, etc. There are exist free software projects
+where part of their history is forever lost because, for example, the project
+moved from Sourceforge to Github, but made no effort (or was unable) to migrate
+issues or somesuch. Linkages between changes and the issues they relate to
+can easily be broken, though at least with mailing lists you can often rewrite
+URLs if you have something consistent like a `Message-Id`.
+
+We talked about how cover notes, pull request messages, etc. can thus also be
+lost to some extent. Is this an argument to always use merges whose message
+bodies contain those details, rather than always fast-forwarding? Or is it a
+reason to encapsulate all those discussions into git objects which can be
+forever associated with the changes in the DAG?
+
+We then diverted into discussion of CI, testing every commit, and the benefits
+and limitations of automated testing vs. manual testing; though I think that's
+a little too off-piste for even this summary. We also talked about how commit
+message audiences include software perhaps, with the recent movement toward
+[conventional commits][ccommits] and how, with respect to commit messages for
+machine readability, it can become very complex/tricky to craft good commit
+messages once there are multiple disparate audiences. For projects the size of
+the Linux kernel this kind of thing would be nearly impossible, but for smaller
+projects, perhaps there's value.
+
+[ccommits]: https://www.conventionalcommits.org/en/v1.0.0/
+
+Finally, we all agreed that we liked the quote at the end of the article, and so
+I'd like to close out by repeating it for you all...
+
+[Hal Abelson][habl] famously said:
+
+> Programs must be written for people to read, and only incidentally for
+> machines to execute.
+
+[habl]: https://en.wikipedia.org/wiki/Hal_Abelson
+
+Jeremy agrees, as do we, and extends that to the metacommit information as
+well.