Hi Denton
On 14/07/2020 04:10, Denton Liu wrote:
Hi Philippe,
On Mon, Jul 13, 2020 at 10:44:06PM -0400, Philippe Blain wrote:
Hello,
I learned today that doing `git rebase --keep-base master`
will drop commits that were cherry-picked from master to the current branch.
I was simply doing a code clean up on my feature branch (the full command was
`git rebase -i --keep-base master`), and this kind of confused me for a moment.
Glad I'm not the only one using this feature :)
Is this a sane default ? I understand that it is a good default when we are rebasing
*on top* of master, but here I'm just doing some squashing and fixup's and I did not
want the commit I had cherry-picked from master to disappear (yet). In fact, because it
was dropped, it created a modify/delete conflict because in a subsequent commit
in my feature branch I'm modifying files that are added in the commit I cherry-picked.
So if I'm not mistaken, if we have the following graph
A - B - C - D (master)
\
- C' - D (feature)
and we do `git rebase --keep-base master` from feature, C' will be
dropped? Indeed, I am surprised by how this interacts with the
default setting of --reapply-cherry-picks.
To me the question is why are we looking at the upstream commits at all
with `--keep-base`? I had expected `rebase --keep-base` to be the same
as `rebase $(git merge-base [--fork-point] @{upstream} HEAD)` but
looking at the code it seems to be `rebase --onto $(git merge-base
@{upstream} HEAD) @{upstream}`. I didn't really follow the development
of this feature - is there a reason we don't just use the merge-base as
the upstream commit?
Best Wishes
Phillip
How would a change that made '--reapply-cherry-picks' be the default when using 'keep-base'
be received ?
I'm somewhat surprised that --no-reapply-cherry-picks is the default. I
would argue that it _shouldn't_ be the default at all. It's an
optimisation for when no --onto or --keep-base are specified but it
definitely can cause problems otherwise, as we've seen.
I think I would argue for the following in decreasing order of
preference:
1. Make --no-reapply-cherry-picks the default in all cases.
(Those who need the optimisation can enable it manually and
we can add a configuration option for it.)
2. Make --no-reapply-cherry-picks only active if no --onto or
--keep-base are given (--keep-base is a special case of --onto
so we only have to handle it in one place).
Tangential question: in any case, would it make sense to still add the "dropped because
already upstream" commits to the todo list, in the case of an interactive rebase ?
(maybe commented out, or listed as 'drop' with some kind of comment saying those
are dropped because they appear textually upstream?)
That would make sense to me. I don't have a preference between either.
Thanks,
Denton
Cheers,
Philippe.
P.S. I CC'd those who were involved with the 'keep-base' patch or the 'reapply-cherry-picks' patch.
