Re: [PATCH 1/2] rebase: help user when dying with preserve-merges`

["Ævar Arnfjörð Bjarmason" <avarab@gmail.com>]

On Tue, Feb 22 2022, Philip Oakley wrote:

> On 22/02/2022 15:32, Ævar Arnfjörð Bjarmason wrote:
>> On Tue, Feb 22 2022, Philip Oakley via GitGitGadget wrote:
>>
>>> From: Philip Oakley <philipoakley@iee.email>
>>>
>>> Git will die if a "rebase --preserve-merges" is in progress.
>>> Users cannot --quit, --abort or --continue the rebase.
>>>
>>> This sceario can occur if the user updates their Git, or switches
>>> to another newer version, after starting a preserve-merges rebase,
>>> commonly via the pull setting.
>>>
>>> One trigger is an unexpectedly difficult to resolve conflict, as
>>> reported on the `git-users` group.
>>> (https://groups.google.com/g/git-for-windows/c/3jMWbBlXXHM)
>>>
>>> Tell the user the cause, i.e. the existence of the directory.
>>> The problem must be resolved manually, `git rebase --<option>`
>>> commands will die, or the user must downgrade. Also, note that
>>> the deleted options are no longer shown in the documentation.
>> I can go and read the linked thread for the answer, but:
>>
>>>  		if (is_directory(buf.buf)) {
>>> -			die("`rebase -p` is no longer supported");
>>> +			die("`rebase --preserve-merges` (-p) is no longer supported.\n"
>>> +			"You still have a `.git/rebase-merge/rewritten` directory, \n"
>>> +			"indicating a `rebase preserve-merge` is still in progress.\n");
>>>  		} else {
>>>  			strbuf_reset(&buf);
>>>  			strbuf_addf(&buf, "%s/interactive", merge_dir());
>> As much of an improvement this is, I'd be no closer to knowing what I
>> should do at this point.
>>
>> Should I "rm -rf" that directory, downgrade my version of git if I'd
>> like to recover my work (as the message alludes to).
>>
>> In either case I'd think that this is getting a bit past the length
>> where we'd have just a die() v.s. splitting it into a die()/advise()
>> pair. I.e. to have the advise() carry some bullet-point list about X/Y/Z
>> solutions, with the die() being a brief ~"we did because xyz dir is
>> still here".
>>
>>
> Hi Ævar,
>
> Exactly. This is a slightly special, but real, case. The previous
> message was essentially totally opaque to users. An "If I were you I
> wouldn't start from here" response is somewhat true, so we simply tell
> the user how they got to receive the fatal message. They can then take
> any of the options they choose.
>
> Ultimately the user downgraded and managed to use "rebase --continue",
> as advised by Git, without the response "fatal:" to complete their old
> preserve-merges rebase.

Right. I'm pointing out that in this proposed version of the die()
message we stop just short of actually telling the user how to proceed.

I.e. just that they have a X directory, not that they should either
remove X and lose their work, or downgrade git, proceed, and then
upgrade git.

> They'll hit a similar fault in short order because when they next `pull`
> they'll be slipped into trying the preserve-merge rebase again - that's
> the 2/2 patch, making sure they know why.

Well, this is "rebase". You can have been running rebases in a
repository without ever having any interactions with remotes.

And even if you had interactions with remotes you might be doing so via
"git fetch" followed by "git rebase", and might not ever invoke "git
pull".

And even if you did a "git pull" later shouldn't the error you got here
be sufficiently stand-alone as to tell you what to do, without needing a
later "pull"?