When I occasionally manually commit with Magit while git-auto-commit-mode is enabled, submitting the commit saves .git/COMMIT_EDITMSG, which seems to trigger git-auto-commit-mode's prompt for a message (since I have gac-ask-for-summary-p enabled). This also happens when modifying ignored files. If I enter a message, I get a warning that the file I tried to commit is ignored.
git-auto-commit-mode should probably ignore .git and ignored files by default, without the user having to set up local variables for every ignored file or subdirectory. Is this possible?