The docs currently say the following:

When you squash commits, by default, GitHub will concatenate all your commit messages to form a unified commit message. This often yields an overly verbose commit message with many unhelpful entries (e.g. "fix typo"). Please double-check (and hand-edit if necessary) your commit message before merging such that the message contains a helpful description of the overall change.

However, it seems that today commits are automatically squashed by GitHub in a way that only preserves the initial commit message, and this warning is no longer necessary.

(Also, I think the docs should explain what "the tree" is. From my understanding, it refers to this git repo.)

I'm creating this issue but I would rather someone else update it/remove it as I'm not sure what it should say and I would need to get it reviewed etc.