Re: [PATCH 3/3] commit: give correct advice for empty commit during a rebase

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

Hi Dscho

On 25/10/2019 12:48, Johannes Schindelin wrote:
> Hi Phillip,
> 
> On Thu, 24 Oct 2019, Phillip Wood wrote:
> 
>> On 23/10/2019 00:30, Johannes Schindelin via GitGitGadget wrote:
>>> From: Johannes Schindelin <johannes.schindelin@gmx.de>
>>>
>>> In dcb500dc16c (cherry-pick/revert: advise using --skip, 2019-07-02),
>>> `git commit` learned to suggest to run `git cherry-pick --skip` when
>>> trying to cherry-pick an empty patch.
>>>
>>> However, it was overlooked that there are more conditions than just a
>>> `git cherry-pick` when this advice is printed (which originally
>>> suggested the neutral `git reset`): the same can happen during a rebase.
>>>
>>> Let's suggest the correct command, even during a rebase.
>>>
>>> While at it, we adjust more places in `builtin/commit.c` that
>>> incorrectly assumed that the presence of a `CHERRY_PICK_HEAD` meant that
>>> surely this must be a `cherry-pick` in progress.
>>>
>>> Note: we take pains to handle the situation when a user runs a `git
>>> cherry-pick` _during_ a rebase. This is quite valid (e.g. in an `exec`
>>> line in an interactive rebase). On the other hand, it is not possible to
>>> run a rebase during a cherry-pick, meaning: if both `rebase-merge/` and
>>> `sequencer/` exist, we still want to advise to use `git cherry-pick
>>> --skip`.
>>
>> Thanks for working on this. It's unfortunate that rebase does not remove
>> CHERRY_PICK_HEAD for empty commits as it does if the commit is not
>> empty.
> 
> Oh, so that's what it is that bites me all the time? I frequently run
> interactive rebases and sometimes mess up authorship (taking authorship
> of patches that I did not, in fact, author). I guess what happens is
> that I `git commit` in the middle of a rebase that was interrupted by
> merge conflicts.

I used to do that a lot, I eventually trained myself not to commit after 
conflicts during a rebase and leave it to `rebase --continue` but it is 
annoying that it does not work

> So I would actually like to see the _exact opposite_ of what you want to
> see: I want to keep `CHERRY_PICK_HEAD` even in the non-empty case.

I don't necessarily object - having it consistent one way or the other 
would be a distinct improvement, it has been removed when there are 
conflicts since it's inception [1] (That's v2 of the series which 
started removing CHERRY_PICK_HEAD in the case of rebase conflicts. I 
couldn't find any discussion of v1 that recommended that change though). 
There is also another thread [2].

[1] 
https://public-inbox.org/git/1297876835-70613-1-git-send-email-jaysoffian@gmail.com/
[2] 
https://public-inbox.org/git/CAMP44s1EAwHjQ7S2ArLvhNg5qkR05DRJ70tQmP8sXYdOP=i_zQ@mail.gmail.com/ 



>> I think this is because 'rebase --continue' will skip an empty commit
>> so the user _has_ to run 'git commit' manually to keep it. If it had
>> been designed so that 'rebase --continue' kept the empty commit and
>> 'rebase --skip' skipped it then we would not have this problem but
>> it's a bit late to worry about that now.
> 
> True.
> 
>> I don't this patch can distinguish between an empty cherry-pick
>> performed by the user while a rebase is in progress and an empty pick
>> performed by rebase as both create CHERRY_PICK_HEAD while
>> .git/rebase-merge exists. It seems to assume that CHERRY_PICK_HEAD was
>> created by rebase and prints advise based on that which may or may not
>> be the correct. I think we could distinguish the two by checking if
>> CHERRY_PICK_HEAD matches .git/rebase-merge/stopped-sha or REBASE_HEAD.
> 
> I guess we could, but then, I would rather worry about that in the next
> cycle. In this cycle, I would rather fix the common case, which is that
> a `git rebase -i` fails and tells me to `git cherry-pick --skip` instead
> of `git rebase --skip`.
> 
> And even if I performed a `git cherry-pick` during a `git rebase` and
> the result would be an empty commit, I'd rather be told to `git rebase
> --skip` to continue...
> 
> But if you feel strongly that this should be fixed differently, I'll
> gladly leave it to you ;-)

I'm happy to wait until the next cycle once we've decided what to do 
about CHERRY_PICK_HEAD during rebases.

Best Wishes

Phillip

> Ciao,
> Dscho
> 
>>
>> Best Wishes
>>
>>
>> Phillip
>>
>>>
>>> Signed-off-by: Johannes Schindelin <johannes.schindelin@gmx.de>
>>> ---
>>>   builtin/commit.c       | 33 ++++++++++++++++++++++++---------
>>>   t/t3403-rebase-skip.sh |  9 +++++++++
>>>   2 files changed, 33 insertions(+), 9 deletions(-)
>>>
>>> diff --git a/builtin/commit.c b/builtin/commit.c
>>> index e588bc6ad3..2beae13620 100644
>>> --- a/builtin/commit.c
>>> +++ b/builtin/commit.c
>>> @@ -59,6 +59,9 @@ N_("The previous cherry-pick is now empty, possibly due to conflict resolution.\
>>>   "    git commit --allow-empty\n"
>>>   "\n");
>>>
>>> +static const char empty_rebase_advice[] =
>>> +N_("Otherwise, please use 'git rebase --skip'\n");
>>> +
>>>   static const char empty_cherry_pick_advice_single[] =
>>>   N_("Otherwise, please use 'git cherry-pick --skip'\n");
>>>
>>> @@ -122,7 +125,7 @@ static enum commit_msg_cleanup_mode cleanup_mode;
>>>   static const char *cleanup_arg;
>>>
>>>   static enum commit_whence whence;
>>> -static int sequencer_in_use;
>>> +static int sequencer_in_use, rebase_in_progress;
>>>   static int use_editor = 1, include_status = 1;
>>>   static int have_option_m;
>>>   static struct strbuf message = STRBUF_INIT;
>>> @@ -183,6 +186,8 @@ static void determine_whence(struct wt_status *s)
>>>   		whence = FROM_CHERRY_PICK;
>>>   		if (file_exists(git_path_seq_dir()))
>>>   			sequencer_in_use = 1;
>>> +		if (file_exists(git_path_rebase_merge_dir()))
>>> +			rebase_in_progress = 1;
>>>   	}
>>>   	else
>>>   		whence = FROM_COMMIT;
>>> @@ -453,8 +458,11 @@ static const char *prepare_index(int argc, const char **argv, const char *prefix
>>>   	if (whence != FROM_COMMIT) {
>>>   		if (whence == FROM_MERGE)
>>>   			die(_("cannot do a partial commit during a merge."));
>>> -		else if (whence == FROM_CHERRY_PICK)
>>> +		else if (whence == FROM_CHERRY_PICK) {
>>> +			if (rebase_in_progress && !sequencer_in_use)
>>> +				die(_("cannot do a partial commit during a rebase."));
>>>   			die(_("cannot do a partial commit during a cherry-pick."));
>>> +		}
>>>   	}
>>>
>>>   	if (list_paths(&partial, !current_head ? NULL : "HEAD", &pathspec))
>>> @@ -950,10 +958,12 @@ static int prepare_to_commit(const char *index_file, const char *prefix,
>>>   			fputs(_(empty_amend_advice), stderr);
>>>   		else if (whence == FROM_CHERRY_PICK) {
>>>   			fputs(_(empty_cherry_pick_advice), stderr);
>>> -			if (!sequencer_in_use)
>>> -				fputs(_(empty_cherry_pick_advice_single), stderr);
>>> -			else
>>> +			if (sequencer_in_use)
>>>   				fputs(_(empty_cherry_pick_advice_multi), stderr);
>>> +			else if (rebase_in_progress)
>>> +				fputs(_(empty_rebase_advice), stderr);
>>> +			else
>>> +				fputs(_(empty_cherry_pick_advice_single), stderr);
>>>   		}
>>>   		return 0;
>>>   	}
>>> @@ -1156,8 +1166,11 @@ static int parse_and_validate_options(int argc, const char *argv[],
>>>   	if (amend && whence != FROM_COMMIT) {
>>>   		if (whence == FROM_MERGE)
>>>   			die(_("You are in the middle of a merge -- cannot amend."));
>>> -		else if (whence == FROM_CHERRY_PICK)
>>> +		else if (whence == FROM_CHERRY_PICK) {
>>> +			if (rebase_in_progress && !sequencer_in_use)
>>> +				die(_("You are in the middle of a rebase -- cannot amend."));
>>>   			die(_("You are in the middle of a cherry-pick -- cannot amend."));
>>> +		}
>>>   	}
>>>   	if (fixup_message && squash_message)
>>>   		die(_("Options --squash and --fixup cannot be used together"));
>>> @@ -1628,9 +1641,11 @@ int cmd_commit(int argc, const char **argv, const char *prefix)
>>>   			reduce_heads_replace(&parents);
>>>   	} else {
>>>   		if (!reflog_msg)
>>> -			reflog_msg = (whence == FROM_CHERRY_PICK)
>>> -					? "commit (cherry-pick)"
>>> -					: "commit";
>>> +			reflog_msg = (whence != FROM_CHERRY_PICK)
>>> +					? "commit"
>>> +					: rebase_in_progress && !sequencer_in_use
>>> +					? "commit (rebase)"
>>> +					: "commit (cherry-pick)";
>>>   		commit_list_insert(current_head, &parents);
>>>   	}
>>>
>>> diff --git a/t/t3403-rebase-skip.sh b/t/t3403-rebase-skip.sh
>>> index 1f5122b632..77b03ac49f 100755
>>> --- a/t/t3403-rebase-skip.sh
>>> +++ b/t/t3403-rebase-skip.sh
>>> @@ -76,4 +76,13 @@ test_expect_success 'moved back to branch correctly' '
>>>
>>>   test_debug 'gitk --all & sleep 1'
>>>
>>> +test_expect_success 'correct advice upon empty commit' '
>>> +	git checkout -b rebase-skip &&
>>> +	test_commit a1 &&
>>> +	test_tick &&
>>> +	git commit --amend -m amended --no-edit &&
>>> +	test_must_fail git rebase -m --onto a1 HEAD^ 2>err &&
>>> +	test_i18ngrep "git rebase --skip" err
>>> +'
>>> +
>>>   test_done
>>>
>>
>>