Re: [RFC/PATCH] stash: Delete MERGE_RR before stash apply

From: Junio C Hamano <gitster@pobox.com>
Date: Jul 6, 2012, 20:01 UTC
Message-ID: <7v7gugodzh.fsf@alter.siamese.dyndns.org>
In-Reply-To: <CABURp0rOfr=c-TcF7O6Ms=2iRA3SC9ckt_ukeozBS5vGqaKZaQ@mail.gmail.com>

Phil Hord <phil.hord@gmail.com> writes:

Show 21 quoted lines

>> Would an obvious alternative of running "git rerere" ourselves after
>> running "git merge-recursive" in this script work?
>>
>>  git-stash.sh | 1 +
>>  1 file changed, 1 insertion(+)
>>
>> diff --git a/git-stash.sh b/git-stash.sh
>> index 4e2c7f8..bbefdf6 100755
>> --- a/git-stash.sh
>> +++ b/git-stash.sh
>> @@ -469,6 +469,7 @@ apply_stash () {
>>         else
>>                 # Merge conflict; keep the exit status from merge-recursive
>>                 status=$?
>> +               git rerere
>>                 if test -n "$INDEX_OPTION"
>>                 then
>>                         gettextln "Index was not unstashed." >&2
>
> Yes, except it needs "git rerere clear".  "git rerere" is not enough
> to cause the clean-up to occur.

Intuitively, it feels wrong to run "rerere clear" after an operation that potentially can create conflicts in the index and in the working tree.

The point in the codepath where the above "git rerere" appears is immediately after we run merge-recursive backend. Because the backend does not invoke rerere itself (which by the way probably is the correct thing not to; I haven't thought things through, though), we invoke it ourselves there, so that the user can ask rerere to replay an earlier conflict resolution. Why can it be a good thing to discard potentially useful information with "git rerere clear"?

I just tried this sequence (manually without any patch).

    $ git init empty && cd empty
    $ for i in a b c d e; do echo $i; done >file
    $ git add file && git commit -m initial
    $ for i in a b C d e; do echo $i; done >file ;# c to C
    $ git stash

    $ for i in a B c d e; do echo $i; done >file ;# b to B
    $ git commit -a -m second

    $ mkdir .git/rr-cache ;# enable rerere
    $ git stash apply ;# conflicts
    $ git rerere ;# records preimage

    $ for i in a B C d e; do echo $i; done >file ;# c to C
    $ git commit -a -m third ;# records resolution
    $ git reset --hard HEAD^

    $ git stash apply ;# conflicts
    $ git rerere ;# replays

I think the above "how about this" patch is equivalent to the two "git rerere" invocations I made manually with my experiment, and it seems to improve the end user experience (please try it yourself).

What am I missing???