Bisect leads to the commit, the commit message explains why the change was made. I take the explanation from 10+ years ago and determine if the reason still applies today.
Or, I bisect and there's a low quality commit from 10 years ago from a person long since departed that simply says "fixup" and I'm dead in the water.
(In case someone points out a comment is more suitable: comments are less likely to survive refactors, and people who write terrible commit messages also tend to be terrible commenters. Informative commit messages supplement good comments.)
Commit messages are far easier to parse and understand compared to a moderate size diff. By reading the commit message before looking at the diff, it really helps in terms of understanding the context of the diff and what to expect.
Commit messages provide intent, and should reference the original change request to see what the commit was intended to fix.
I would say the whole chain matters.
A good change request (Jira) with defects, and how to recreate the fault, as well as relevant requirements (by reference, not cut-n-paste)
Good comments on the code that is changing. Don't document the defect and how you fixed it, just comment what the code does (if the code is not perfectly clear),
Then a good commit message, referencing the change request, to tie it all together.
It all matters.
Commit messages aren't mutually exclusive to the inline documentation.
I am making the case that inline documentation is far more important than commit messages.
Git was made with the intention that commit messages look like whole emails, describing not only why the change was made but also the thought process behind it, why this particular solution was chosen instead of some other etc.
What you describe is a decent header, although most people would probably prefer "Add ability to" (not "Added ability to", this is a custom that goes way back before git).
Inline documentation, or comments, is something else entirely. That is a moving target that can describe intended usage, remote APIs, and hard to understand passages. Commit messages describes a particular changeset, at a fixed point in time.
Google it, and see that most people's ideas of a good commit message goes way beyond the header ("shortlog") line.
If you use markdown Syntax in your commit body, github and other tools will gladly render it correctly. You can grep for commit messages with "git log --grep <pattern>" and it will also search commit bodies as well. It's beautiful!
When additional detail is helpful about the motivation for or gotchas related to a commit, starting a new paragraph and elaborating there is totally fine.
But I agree with you, they aren't mutually exclusive to inline documentation. The inline documentation is more important when the explanation is relevant to understanding the code which results from the commit, whereas a clear commit message is more important when the information is to illuminate the reasons for (or history surrounding) the change itself.
This also follows what I've seen at a few companies since then. Would you say that's a general rule?
There was only used by one person who gave no context on why he used that format, so it's probably no coincidence in such an example that to me the extra structure seemed to add only opacity and no real value.
I can absolutely imagine that being different in a company that used this convention widely and built tooling around it. Doubly so when a lot of the staff is junior enough that it's helpful guidance for structuring thoughts around what the commit does.
Though, I'm not sure it's a helpful restriction for commits that clarify, refactor, or clean up code. One can certainly reference an issue tracker number as the {feature/bug} element that gives the necessary context, but the strictness spreads the information around more widely than is natural.
If someone was adopting that convention as a workaround for helping team members learn how to communicate, they're probably going to find that it's a very incomplete workaround.
When merging you can pretty easily see what ticket each commit was for. Seems superfluous to put the same information in every commit messages.
By contrast, referencing the ticket number (but not necessarily ticket title) is common practice in the PR message, and seems much more helpful.
Commit messages are about the change, whereas comments are about the state of the code.
You are assuming here that all programmers even "do" git. A lot don't. A whole lot of them. I worked with some companies that would have some horrible horrible version control system only and I just wanted to cry. Sure, git has its warts, but once you get it, it's a tool that can be _incredibly_ productive. I hate having good tools taken away.
I read them quite often. Whenever there is a regression detected between 2 software revisions that have been deployed somewhere the first thing I do is checking commits and commit messages for packages that have changed to find the more obvious reasons for a behavior difference. Checking code diffs at that point would be a lot more effort.
You're projecting. YOU never read them. I used to be the same way. Now I see other people reading them and I've started to myself. I follow other people's efforts and progress. It's a great way to learn not only the code but to communicate better.
Is there any data to support your or his claim as more representative of the population?
Do people not use git blame to check what they're changing before they change it? That's how I check the history around the changes I'm going to make before I make them.
And am frequently disappointed.
The comments I put in commits are things you'd be horrified to see littering your codebase (though I did it that way once upon a time too). They are the "whys" behind a change. Sometimes they have relatively little to do with individual lines of code, and don't need to be maintained like comment blocks should be. The temporal binding is absolutely intended.
Comments are often wrong, for the wrong reasons. People that change code, but don't update the comments to reflect the code change are evil. But then, people that put to much superfluous information in comments, that should just be left to the code, are also evil.
BTW, if your code implements a part of a standard, try putting the standard, and what subsection, your code addresses. Just the reference not the text. 802.11G for example (old fart) or TA55, or RFC 1536. Whatever. Then list the date of the document and the subsection.
I had to modify a Reed-Solomon implementation many years ago, and the original two authors based the implementation on a particular textbook. They gave the ISBN and then chapter/paragraph/table/illustration references on each block. I went and got a copy of the book, and it all lined up perfectly. Best documented code I have ever encountered.
Writing good comments is far more important. Don't explain what the code does - that's what the code is for, explain the why and the background information in the code. Additional, explain what the code does at the function level or at the module level - at a much higher abstraction level basically than the line of the code.
No one ever looks at the commit messages when trying to figure out what the code does as it convolves history and state of the repository, having to contextually wrap your head around when and how this commit was added.
Inline documentation? Perfect.