Re: [PATCH] cherry-pick: do not error on non-merge commits when '-m 1' is specified

From: Junio C Hamano <gitster@pobox.com>
Date: Dec 13, 2018, 04:20 UTC
Message-ID: <xmqqo99qf46q.fsf@gitster-ct.c.googlers.com>
In-Reply-To: <871s6n5mtd.fsf@javad.com>

Sergey Organov <sorganov@gmail.com> writes:

Show 8 quoted lines

> When cherry-picking multiple commits, it's impossible to have both
> merge- and non-merge commits on the same command-line. Not specifying
> '-m 1' results in cherry-pick refusing to handle merge commits, while
> specifying '-m 1' fails on non-merge commits.
>
> This patch allows '-m 1' for non-merge commits. Besides, as mainline is
> always the only parent for a non-merge commit, it made little sense to
> disable it in the first place.

The feature to give a range to cherry-pick came much much later in 7e2bfd3f ("revert: allow cherry-picking more than one commit", 2010-06-02) that first appeared in v1.7.2. The feature to allow picking a merge commit came in 7791ecbc ("revert/cherry-pick: work on merge commits as well", 2007-10-23), first appeared in v1.5.4.

In the original context to pick a single commit, it made perfect sense to avoid mistakes by blindly passing '-m 1' to non-merge commit. It may be fair to say that we failed to reconsider what to do with '-m 1' when we did 7e2bfd3f, but it is utterly an unfair history revisionism to say that it made little sense to disable it in the first place.

The change to the code itself looks sane, but applying this patch alone will break existing tests whose expectations must be updated, and this new behaviour must be protected by a new test (or two) so that we won't accidentally stop accepting "-m 1" for a single-parent commit.

Thanks.

Show 25 quoted lines

> Signed-off-by: Sergey Organov <sorganov@gmail.com>
> ---
>  sequencer.c | 10 +++++++---
>  1 file changed, 7 insertions(+), 3 deletions(-)
>
> diff --git a/sequencer.c b/sequencer.c
> index e1a4dd1..d0fd61b 100644
> --- a/sequencer.c
> +++ b/sequencer.c
> @@ -1766,9 +1766,13 @@ static int do_pick_commit(enum todo_command command, struct commit *commit,
>  			return error(_("commit %s does not have parent %d"),
>  				oid_to_hex(&commit->object.oid), opts->mainline);
>  		parent = p->item;
> -	} else if (0 < opts->mainline)
> -		return error(_("mainline was specified but commit %s is not a merge."),
> -			oid_to_hex(&commit->object.oid));
> +	} else if (1 < opts->mainline)
> +		/*
> +		 *  Non-first parent explicitly specified as mainline for
> +		 *  non-merge commit
> +		 */
> +		return error(_("commit %s does not have parent %d"),
> +			     oid_to_hex(&commit->object.oid), opts->mainline);
>  	else
>  		parent = commit->parents->item;