[diek]

The golden rule is "do not rewrite history of a public branch". Rebase/squash your PR branches to your heart's content, but once it's merged that's it.

You get clean history by not merging branches with 50 intermediary "fiddling with X" commits in them.

[btilly]

Related, it is a bad idea to use long-running per team branches. Merge early, merge often, get commits to trunk ASAP. With best practices on unit testing, code review, and so on, this scales to many thousands of developers. And will save a lot of pain over time.