The commit queue does not support multi-line commit messages. Currently users pass a --message argument, which becomes the commit message.
In the GitHub-backed commit queue, supporting arbitrary commit messages is trivial, because we are relying on GitHub's own mechanisms for merging, and GitHub has access to the actual prospective commits.
In the CLI commit queue, however, the current implementation does not have access to the actual commits. We explored using git am and initially rejected it as an option, since using it does not work with the way Evergreen renders diffs. (There may have been another reason, which I do not remember.)
However, Eric Milkie pointed out 2 problems with our current approach
1. Developers are used to squashing their own commits. The current model of shipping a diff of the entire set of commits means that users can no longer push a set of commits at once.
2. The commit queue does not support multi-line commit messages. It is also awkward that a user writes a commit message and then must rewrite that message on the command line.
Jonathan Brill, David Bradford - I'd appreciate any additional thoughts you have about this, including how we might improve this, and how important you feel it would be to improve this before we roll out the commit queue.