Re: [PATCH] rebase -i: avoid checking out $branch when possible

Shezan Baig [off-list ref] writes:

Just wondering if this patch is going to be available in an upcoming
version of git?

As we can see from the exchange you quoted, I do not think we have nailed
the details of desired behaviour in the updated code down.

Thomas, how would you want to proceed?

Junio C Hamano [off-list ref] writes:

Shezan Baig [off-list ref] writes:

quoted

Just wondering if this patch is going to be available in an upcoming
version of git?

As we can see from the exchange you quoted, I do not think we have nailed
the details of desired behaviour in the updated code down.

Thomas, how would you want to proceed?

Hrm.  You wrote:

The discrepancy in the "abort" case may come only in the three cases:

 - EDITOR is pointing at something funny, [let's do the checkout to be
   safe for scripts]

Agreed.

 - The user told us not to do the rebase by making insn sheet empty.  In
   other words, this is "aborting the entire rebase", so ideally it
   should come back to the state before the user ran "git rebase"
   command (i.e. where she was before we switched to <branch>).

   I do not think this ideal behaviour is something neither batch or
   interactive rebase has traditionally implemented, but I can see how
   we can sell this as a bugfix to the end users.

That's a convincing argument, so let's make it so.

 - It turns out that everything is already contained and there is
   nothing to apply, i.e. after this sequence:

	git checkout branch
	git checkout $onto_or_merge_base_between_base_and_branch

   we find out that "git cherry $onto_or_merge_base branch" is empty.

Is there a command missing here?  This alone does not make them the
same, perhaps you meant some resetting.

I'll assume that you meant a case where the user is *not* on branch, but
base/onto is an ancestor of the branch, e.g., in a sequence

  git checkout base
  git reset --hard branch~5
  # now branch..base is empty
  git rebase base branch

the rebase will not do anything unless forced.  Similarly for the case
where base==branch.  And then

   Because you will be one commit ahead of $onto_or_merge_base if "git
   cherry" were to give one commit to be replayed, I think it is
   logically correct if you stayed at the $onto_or_merge_base without
   checking out <branch>.  In other words, abort-with-checkout is not
   ideal for this case; we would want to just abort in this case.

This would be hard to sell, because a script that runs

  git rebase base branch

could reasonably assume that after the rebase, the current branch is
'branch', unless some error occurred.  And we'd be breaking that.

Or am I missing the point of your reasoning?

-- 
Thomas Rast
trast@{inf,student}.ethz.ch