Re: [PATCH] t3424: new rebase testcase documenting a stat-dirty-like failure

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

Hi Elijah

On 17/02/2020 19:12, Elijah Newren wrote:
> I forgot to add some cc's in GitGitGadget before submitting; adding now...
> 
> On Mon, Feb 17, 2020 at 9:15 AM Elijah Newren via GitGitGadget
> <gitgitgadget@gmail.com> wrote:
>>
>> From: Elijah Newren <newren@gmail.com>
>>
>> A user discovered a case where they had a stack of 20 simple commits to
>> rebase, and the rebase would succeed in picking the first commit and
>> then error out with a pair of "Could not execute the todo command" and
>> "Your local changes to the following files would be overwritten by
>> merge" messages.
>>
>> Their steps actually made use of the -i flag, but I switched it over to
>> -m to make it simpler to trigger the bug.  With that flag, it bisects
>> back to commit 68aa495b590d (rebase: implement --merge via the
>> interactive machinery, 2018-12-11), but that's misleading.  If you
>> change the -m flag to --keep-empty, then the problem persists and will
>> bisect back to 356ee4659bb5 (sequencer: try to commit without forking
>> 'git commit', 2017-11-24)
>>
>> After playing with the testcase for a bit, I discovered that added
>> --exec "sleep 1" to the command line makes the rebase succeed, making me
>> suspect there is some kind of discard and reloading of caches that lead
>> us to believe that something is stat dirty, but I didn't succeed in
>> digging any further than that.

Intriguing - it's strange that it errors out picking commit2, not 
commit1 I'll try and have a look at it. There seem to be some leftover 
bits at the start of the test that want removing see below

>> Signed-off-by: Elijah Newren <newren@gmail.com>
>> ---
>>      t3424: new rebase testcase documenting a stat-dirty-like failure
>>
>>      A user discovered a case where they had a stack of 20 simple commits to
>>      rebase, and the rebase would succeed in picking the first commit and
>>      then error out with a pair of "Could not execute the todo command" and
>>      "Your local changes to the following files would be overwritten by
>>      merge" messages.
>>
>>      Their steps actually made use of the -i flag, but I switched it over to
>>      -m to make it simpler to trigger the bug. With that flag, it bisects
>>      back to commit 68aa495b590d (rebase: implement --merge via the
>>      interactive machinery, 2018-12-11), but that's misleading. If you change
>>      the -m flag to --keep-empty, then the problem persists and will bisect
>>      back to 356ee4659bb5 (sequencer: try to commit without forking 'git
>>      commit', 2017-11-24)
>>
>>      After playing with the testcase for a bit, I discovered that added
>>      --exec "sleep 1" to the command line makes the rebase succeed, making me
>>      suspect there is some kind of discard and reloading of caches that lead
>>      us to believe that something is stat dirty, but I didn't succeed in
>>      digging any further than that.
>>
>> Published-As: https://github.com/gitgitgadget/git/releases/tag/pr-git-712%2Fnewren%2Fdocument-rebase-failure-v1
>> Fetch-It-Via: git fetch https://github.com/gitgitgadget/git pr-git-712/newren/document-rebase-failure-v1
>> Pull-Request: https://github.com/git/git/pull/712
>>
>>   t/t3424-rebase-across-mode-change.sh | 52 ++++++++++++++++++++++++++++
>>   1 file changed, 52 insertions(+)
>>   create mode 100755 t/t3424-rebase-across-mode-change.sh
>>
>> diff --git a/t/t3424-rebase-across-mode-change.sh b/t/t3424-rebase-across-mode-change.sh
>> new file mode 100755
>> index 00000000000..4d2eb1dd7c6
>> --- /dev/null
>> +++ b/t/t3424-rebase-across-mode-change.sh
>> @@ -0,0 +1,52 @@
>> +#!/bin/sh
>> +
>> +test_description='git rebase across mode change'
>> +
>> +. ./test-lib.sh
>> +
>> +test_expect_success 'setup' '
>> +       rm -rf ../stupid &&
>> +       git init ../stupid &&
>> +       cd ../stupid &&

I think these 3 lines must be left over from you trying this out before 
making it a test

Best Wishes

Phillip

>> +       mkdir DS &&
>> +       >DS/whatever &&
>> +       git add DS &&
>> +       git commit -m base &&
>> +
>> +       git branch side1 &&
>> +       git branch side2 &&
>> +
>> +       git checkout side1 &&
>> +       git rm -rf DS &&
>> +       ln -s unrelated DS &&
>> +       git add DS &&
>> +       git commit -m side1 &&
>> +
>> +       git checkout side2 &&
>> +       >unrelated &&
>> +       git add unrelated &&
>> +       git commit -m commit1 &&
>> +
>> +       echo >>unrelated &&
>> +       git commit -am commit2
>> +'
>> +
>> +test_expect_success 'rebase changes with the apply backend' '
>> +       test_when_finished "git rebase --abort || true" &&
>> +       git checkout -b apply-backend side2 &&
>> +       git rebase side1
>> +'
>> +
>> +test_expect_failure 'rebase changes with the merge backend' '
>> +       test_when_finished "git rebase --abort || true" &&
>> +       git checkout -b merge-backend side2 &&
>> +       git rebase -m side1
>> +'
>> +
>> +test_expect_success 'rebase changes with the merge backend with a delay' '
>> +       test_when_finished "git rebase --abort || true" &&
>> +       git checkout -b merge-delay-backend side2 &&
>> +       git rebase -m --exec "sleep 1" side1
>> +'
>> +
>> +test_done
>>
>> base-commit: e68e29171cc2d6968902e0654b5687fbe1ccb903
>> --
>> gitgitgadget