Our team is deciding on what merge strategy to use in our repo. We're looking at squash merges for the ability to have a clean commit history. However, we want to be able to review intermediate changes if we want more detail on a particular commit - in particular, the intermediate commits on the PR that were squashed.
Normally, squashing and deleting the branch will remove all references to those intermediate commits in the reflog and git garbage collection could clean those up. However, in looking at other repos, it seems like GitHub still retains those intermediate commits.
What we're looking for is confirmation that GitHub is retaining those commit IDs in the reflog and that we're guaranteed they'll stick around. Alternatively, information telling us that's not guaranteed is also good.