How do I change a commit message?

The most recent commit: leave nothing staged and press the amend button under the Working Copy message field. The review opens with the existing message, or your draft if you have written one. Edit the text there, then choose Amend Commit. Show Original lets you compare it with the old message before confirming.

The commit is replaced only when you confirm. See amending to include staged changes too.

Anything older: Innesta has no editor for a message further back. Changing one means rewriting every commit after it, because a commit id is a hash of its message along with everything else — so the commit changes, and so does every commit that has it as an ancestor.

That is an interactive rebase, which is a command line job:

git rebase -i <commit-before-the-one-you-want>

Innesta notices the repository changing underneath it and reloads, so the rewritten history is there when you come back to the window.