Re: [PATCH] rebase --merge: optionally skip upstreamed commits

> When rebasing against an upstream that has had many commits since the
> original branch was created:
>
>  O -- O -- ... -- O -- O (upstream)
>   \
>    -- O (my-dev-branch)
>
> because "git rebase" attempts to exclude commits that are duplicates of
> upstream ones, it must read the contents of every novel upstream commit,
> in addition to the tip of the upstream and the merge base. This can be a
> significant performance hit, especially in a partial clone, wherein a
> read of an object may end up being a fetch.
>
> Add a flag to "git rebase" to allow suppression of this feature. This
> flag only works when using the "merge" backend.