Re: `BUG: sequencer.c:921: GIT_AUTHOR_DATE missing from author script` when trying to reword in interactive rebase

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

On 02/11/2021 01:27, Jeff King wrote:
> On Tue, Nov 02, 2021 at 12:17:29AM +0100, Jonas Kittner wrote:
> 
>> In the interactive prompt I changed `pick` to `reword`, saved and closed the
>> prompt.
>> Commands to repoduce see below
> 
> Thanks for the easy reproduction. Here are commands that slightly
> simplify / automate things, which I used to bisect:
> 
>    rm -rf repo
>    git init repo
>    cd repo
>    git commit --allow-empty -qm base
> 
>    touch file
>    git add .
>    GIT_AUTHOR_DATE='@123456789 +0000' git commit -qm "this message says pick"
> 
>    GIT_EDITOR='sed -i s/pick/reword/' \
>    git.compile rebase -i --committer-date-is-author-date HEAD^
> 
>    # not strictly necessary, but when it works, you can see that the
>    # timestamps correctly match, and that "pick" was changed to "reword"
>    # in the message. Of course when it doesn't work, rebase aborts, so
>    # that's easier to see than looking at the commit. :)
>    git cat-file commit HEAD
> 
>> What happened instead? (Actual behavior)
>> segfault: `BUG: sequencer.c:921: GIT_AUTHOR_DATE missing from author script`
>>
>> [...]
>>
>> https://github.com/git/git/commit/7573cec52c0274ceb166c425be4288f6b3103d6f#d
>> iff-0e574dc9087fc7831bbc1403545a8561f08869576c1ccc4146aa276146ff9777R888-R88
>> 9
>> this seems to be not the case and needs to be handled differently I guess?
> 
> It looks like things did work back in 7573cec52c (rebase -i: support
> --committer-date-is-author-date, 2020-08-17). Bisecting shows that it
> broke in baf8ec8d3a (rebase -r: don't write .git/MERGE_MSG when
> fast-forwarding, 2021-08-20). +cc Phillip (who wrote both commits).

Thanks for bisecting, I think I know what the problem is, I'll post a 
fix tomorrow.

Best Wishes

Phillip