[lolinder]

The first line of the commit message isn't about including information that couldn't be gleaned from the commit. That can be done in subsequent lines. The first line is for two purposes:

* Priming the reader so they are able to quickly interpret what they're seeing when they open the commit.

* Making it easy to search or scan for a specific change.

The last commit message in my example would probably have included the name of the feature as well as the ticket number, but I couldn't be bothered to invent an actual feature name.

DRY doesn't really apply to technical writing, at least not as extremely as you seem to think it should. Headings are supposed to summarize the contents, and that's what commit messages are: headings.

[krainboltgreene]

> Making it easy to search or scan for a specific change.

I'm trying to imagine the near infinite terms I would have to search for to find the commit where I "changed from a hash to a set".

Regardless, every other thing you said could also just be done in the central PR body (and thus the merge commit) and be much easier to access.

Instead of "priming the reader" it's infinitely more helpful to tell the reader why you did something, because you can't extract that from a diff.

[lolinder]

> Instead of "priming the reader" it's infinitely more helpful to tell the reader why you did something, because you can't extract that from a diff.

Again, that can go in the PR body or in subsequent lines. You have ~50 characters in that first line, which is never going to be enough to fully explain anything.

I'm also not suggesting that you eliminate the PR body: that should also include more context. All I'm suggesting is that taking the trouble to organize your commits into discrete units helps reviewers to understand how you perceive the various changes in a single PR as being related to one another, and no amount of text in the PR body will provide the same benefit as being able to look at several distinct diffs containing related changes.