I never understood this philosophy. What makes Git more eternal than any other technology? Why is putting all of your data in one monolithic tool a good solution?
You might change your issue tracking solution. You might change your host solution. You might change your review platform. You might also change your VCS solution. Nothing is eternal.
The commit message itself is way more eternal than GitHub ephemera. There's plenty of old codebases in git that were imported from SVN (or even older RCSes) with all commits intact. What's likely not intact is data in ancient issue trackers from decades past. git is a DVCS, so anyone can clone the repo and get all the commit information. Cloning the issues and such is not nearly so trivial, and isn't a part of the git protocol itself so there's no guarantee it's in any kind of interchangeable format.
Important information should not just be in PR comments. It should be added into the commit information itself so that it'll be maximally available going forward. A good, fully explanatory commit message is a huge asset, and those commit messages will exist for the entire lifetime of the codebase. Anything else, not so much.
I didn't say anything about git. I said the commit messages are eternal, and none of those changes will change the commit messages (except, perhaps, changing the VCS, but usually that will preserve commit messages too).
You'd be foolish to do a VCS migration that discards the commit messages. I've never seen it happen personally, as people tend not to be that foolish. I've worked with legacy codebases that went from CVS -> SVN -> git and all of the commit messages going back to the very beginning are intact, because why would you ever do a migration that doesn't maintain them?
This is a really convincing argument. I was with the parent commenter until I read this; I was like, this is totally PR stuff! But hadn't considered offline situations, or host switches. Thanks op!
Plus, what if you want to know what happened and you're simply offline? Let's not unnecessarily break the D in DVCS.