Re: [PATCH] rebase --abort: cleanup refs/rewritten

[Phillip Wood <phillip.wood123@gmail.com>]

Hi Dscho

On 30/04/2019 23:49, Johannes Schindelin wrote:
> Hi Phillip,
> 
> On Tue, 30 Apr 2019, Phillip Wood wrote:
> 
>> On 29/04/2019 17:07, Johannes Schindelin wrote:
>>>
>>> On Fri, 26 Apr 2019, Phillip Wood wrote:
>>>
>>>> From: Phillip Wood <phillip.wood@dunelm.org.uk>
>>>>
>>>> When `rebase -r` finishes it removes any refs under refs/rewritten
>>>> that it has created. However if the rebase is aborted these refs are
>>>> not removed. This can cause problems for future rebases. For example I
>>>> recently wanted to merge a updated version of a topic branch into an
>>>> integration branch so ran `rebase -ir` and removed the picks and label
>>>> for the topic branch from the todo list so that
>>>>       merge -C <old-merge> topic
>>>> would pick up the new version of topic. Unfortunately
>>>> refs/rewritten/topic already existed from a previous rebase that had
>>>> been aborted so the rebase just used the old topic, not the new one.
>>>>
>>>> Signed-off-by: Phillip Wood <phillip.wood@dunelm.org.uk>
>>>> ---
>>>
>>> Makes a ton of sense, and I feel a bit embarrassed that I forgot about
>>> that item on my TODO list. The patch looks obviously correct!
>>
>> Thanks, after I sent it I realized that --quit should probably clear
>> refs/rewritten as well, so I'll re-roll with that added. (One could argue that
>> a user might want them after quitting the rebase but there is no way to clean
>> them up safely once we've deleted the state files and I suspect most users
>> would be suprised if they were left laying around)
> 
> I am not so sure. `--quit` is essentially all about "leave the state
> as-is, but still abort the rebase".

I think it depends on what you mean by "state" `--quit` is about 
removing state specific to rebases while preserving HEAD, the index and 
worktree. When "rebase --quit" was introduced in 9512177b68 ("rebase: 
add --quit to cleanup rebase, leave everything else untouched", 
2016-11-12) the start of the log message reads

     rebase: add --quit to cleanup rebase, leave everything else untouched

     There are occasions when you decide to abort an in-progress rebase and
     move on to do something else but you forget to do "git rebase --abort"
     first. Or the rebase has been in progress for so long you forgot about
     it. By the time you realize that (e.g. by starting another rebase)
     it's already too late to retrace your steps. The solution is normally

         rm -r .git/<some rebase dir>

     and continue with your life.


So `--quit` is used when the user has forgotten to run "rebase --abort". 
They have moved onto something else and want to remove the rebase state 
without changing the current HEAD, index or worktree, they are not 
looking to use the refs under refs/rewritten. I think the refs rebase 
creates under refs/rewritten is an implementation detail of "rebase -r" 
and should be treated like files under .git/rebase-merge. I'm worried 
that if we leave them lying around after --quit they will cause trouble 
for future rebases in the same way they have after "rebase --abort"

Best Wishes

Phillip

> So if I were you, I would *not* remove the `refs/rewritten/` refs in the
> `--quit` case.
> 
> Ciao,
> Dscho
>