Re: [PATCH 1/2] [GSOC] cherry-pick: fix bug when used with GIT_CHERRY_PICK_HELP

From: Junio C Hamano <gitster@pobox.com>
Date: Jul 29, 2021, 20:56 UTC
Message-ID: <xmqqzgu43kkz.fsf@gitster.g>
In-Reply-To: <5c5ec310b9230ee19bde4b3c8733b359d5218b32.1627561665.git.gitgitgadget@gmail.com>

"ZheNing Hu via GitGitGadget" <gitgitgadget@gmail.com> writes:

Show 20 quoted lines

> -static void print_advice(struct repository *r, int show_hint,
> -			 struct replay_opts *opts)
> +static char *check_need_delete_cherry_pick_head(struct repository *r)
>  {
>  	char *msg = getenv("GIT_CHERRY_PICK_HELP");
>  
>  	if (msg) {
> -		fprintf(stderr, "%s\n", msg);
>  		/*
>  		 * A conflict has occurred but the porcelain
>  		 * (typically rebase --interactive) wants to take care
> @@ -411,18 +409,22 @@ static void print_advice(struct repository *r, int show_hint,
>  		 */
>  		refs_delete_ref(get_main_ref_store(r), "", "CHERRY_PICK_HEAD",
>  				NULL, 0);
> -		return;
> +		return msg;
>  	}
> +	return NULL;
> +}

The patch is a bit hard to read, but I do not think this improves the root cause of the issue at all, which is that "do we need to delete the pseudoref?" decision is tied to and based on the presense of the custom message in the environment variable.

The original issue was that we declared (erroneously) that the presence of a custom message _means_ the caller is not a human but a sequencing machinery that wants to deal with what is done via the CHERRY_PICK_HEAD pseudoref itself, and your original issue was that when a human user has the custom message envirnoment (either on purpose or by mistake), the logic _misidentifies_ the call as if it is made from a sequencing machinery and we lose the CHERRY_PICK_HEAD pseudoref. The root cause is mistaking the correlation (sequencing machinery uses the environment and it also does not want pseudoref) as the causation (presense of the environment means we should remove pseudoref).