From: Phillip Wood <phillip.wood123@gmail.com>
Date: Thu, 15 Dec 2022 15:40:13 GMT
Subject: Re: [RFC PATCH 0/1] rebase --onto detection of already applied commits
Message-ID: <3c5cb346-e6b4-7b85-6d3e-4b625cc21a94@dunelm.org.uk>
In-Reply-To: <9e06bfd1-3e63-2414-e18c-6901fbb290e3@collabora.com>

Hi Cristian

On 13/12/2022 15:34, Cristian Ciocaltea wrote:
> Hi Phillip,
> 
> On 12/13/22 15:04, Phillip Wood wrote:
>> Hi Christian
>>
>> On 13/12/2022 10:37, Cristian Ciocaltea wrote:
>>> Currently '--onto' works as if the user provided the 
>>> '--reapply-cherry-picks' flag,
>>
>> --onto does not affect the cherry-pick detection. When running
>>
>>      git rebase --onto new-base upstream feature
>>
>> any commits in upstream have been cherry-picked from feature they will 
>> not be rebased. What it does not do is look for cherry-picks in 
>> onto...feature. It would be nice to add that but I'm not sure it is 
>> straight forward to do so and still exclude commits that have been 
>> cherry-picked from feature to upstream.
> 
> The proposed patch enables looking for commits into new-base..feature 
> range and excluding the ones reachable from upstream. Since this is a 
> change in the existing behavior, we might need to introduce a new flag 
> to enable it. I previously suggested to use '--no-reapply-cherry-picks' 
> for this purpose, but now it's pretty obvious this will be a source of 
> confusion, since the "cherry-picks" term refers to the commits picked 
> from feature to upstream instead of new-base, as you already mentioned.
> 
> I agree it would be nice to support both exclusion ranges, but I'm not 
> sure how complicated the implementation would be, since I don't have any 
> previous experience with the Git internals. Could this be added as a 
> separate feature at a later point?

If we can I'd rather add code that excludes cherry-pick both ranges. To 
remove the cherry-picks that are in upstream and new-base you could 
rework the todo list generation as follows

1. Calculate the merge-base $mb of feature and upstream
2. Store the list of commits $mb..feature in an array and in a hash
    table indexed their patch-id.
3. Walk $mb..upstream calculating the patch-id for each commit and
    removing any commit in the list from step 2 that matches.
4. If onto is equal to upstream skip to step 7
5. Calculate the merge-base $mb of feature and onto.
6. Walk $mb..new-base calculating the patch-id for each commit and
    removing any commit in the list from step 2 that matches.
7. Generate the todo list using the modified list of commits from step
    2.

I don't have much time at the moment but I can try and help a bit more 
in the New Year if you want.

Best Wishes

Phillip