From mboxrd@z Thu Jan  1 00:00:00 1970
From: Jonathan Nieder <jrnieder@gmail.com>
Subject: Re: [WIP PATCH] revision-walk: --parent option to find children of
 a parent
Date: Thu, 30 Sep 2010 09:32:34 -0500
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References: <99aa4cd5a60b2b2d3eae962acb8a49c2a62a8f77.1285842569.git.git@drmicha.warpmail.net>
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To: Michael J Gruber <git@drmicha.warpmail.net>
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Hi,

Michael J Gruber wrote:

> Introduce a new --parent=<commit> option for the revision walker which
> limits the commits to those which have <commit> as one of their parents.

So this lists the direct children for a given commit.  Could you
mention a use case?  Why would one want to use this instead of

 the_commit=$(git rev-parse --verify <commit>) &&
 git rev-list --parents ... ^<commit> |
 grep -F " $the_commit"

?
 
> --- a/revision.c
> +++ b/revision.c
> @@ -1149,6 +1149,7 @@ static int handle_revision_opt(struct rev_info *revs, int argc, const char **arg
>  {
>  	const char *arg = argv[0];
>  	const char *optarg;
> +	unsigned char sha1[20];

Could this be given narrower scope?

> @@ -1989,6 +1999,14 @@ enum commit_action get_commit_action(struct rev_info *revs, struct commit *commi
>  		return commit_ignore;
>  	if (revs->merges_only && !(commit->parents && commit->parents->next))
>  		return commit_ignore;
> +	if (revs->parent_list) {
> +		struct commit_list *a, *b;
> +		for (b = revs->parent_list; b; b = b->next)
> +			for (a = commit->parents; a; a = a->next)
> +				if (!hashcmp(b->item->object.sha1, a->item->object.sha1))
> +					return commit_show;
> +		return commit_ignore;
> +	}

The implementation looks good.