Potential improvements for partial/shallow clones

[Rudxain]

Important

disclaimer: I've only searched the codebase, I haven't actually used this software (yet)

I assume there's no feature for doing a partial or shallow clone, but if such feature were to be added, I have tips to share:

• If the user has a shallow clone, warn them before amending the grafted commit. Amending such commits will break the history
• If the user wants to do a shallow-clone, it's likely they also want to apply a --filter to it. Git allows clones to be shallow and partial at the same time. I have minimal experience with such repos, but everything is fine so far!
• Before computing the blame of a file in a partial-clone, use backfill to fetch the blobs+trees faster. I guess Git doesn't do this by default because backfill is experimental (according to the manpage)
• When rebasing 2 branches in a partial-clone, use --reapply-cherry-picks to avoid "infinite" loops