I am working on a project in a subversion repository with a strict check-in policy which includes: Every commit to the trunk has to be reviewed by another developer and this mus
Yes, you can rewrite the commit messages. Yes, you can just squash them all in to a single commit. This probably depends on the review process and how much you're doing at once.
"Manually" moving each change to the master branch wouldn't be especially different from rewriting your commit messages at some level, but many diverging branches and cherry-picks could come in handy.
Overall, the answer is "it depends" and "Git is flexible enough to do just about whatever you need".