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

[Philip Oakley <philipoakley@iee.email>]

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.

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.

Philip