Policy on Git commit messages in CONTRIBUTING

Policy on Git commit messages in CONTRIBUTING

I've never been comfortable with constructing or editing commit
messages that will appear under someone else's name, but on the other
hand I don't want to be forced either to use someone else's message
untouched or to remove their name from the "Author" field.  Allowing
myself to make clearly-marked edits seems to be a good compromise, and
square brackets are a common way of marking edits and editorial
comments.