Re: [PATCH v2 1/2] builtin/checkout: simplify metadata initialization

From: Junio C Hamano <gitster@pobox.com>
Date: May 21, 2020, 17:35 UTC
Message-ID: <xmqq1rndtcmd.fsf@gitster.c.googlers.com>
In-Reply-To: <20200521020712.1620993-2-sandals@crustytoothpaste.net>

"brian m. carlson" <sandals@crustytoothpaste.net> writes:

> ...  The only case in which we do not have a commit object is when
> invoking git switch with --orphan.  Moreover, we can only hit this code
> path without a commit object additionally with either --force or
> --discard-changes.

It was easy for me to trace the codepath to see when these options are used we end up with no commit object, but I ran out of time trying to see if the "forced orphan" is the only way to end up with a NULL in new_branch_info->commit. Assuming that is true, of course the following perfectly makes sense.

Show 10 quoted lines

> In such a case, there is no point initializing the checkout metadata
> with a commit or tree because (a) there is no commit, only the empty
> tree, and (b) we will never use the data, since no files will be smudged
> when checking out a branch with no files.  Pass the all-zeros object ID
> in this case, since we just need some value which is a valid pointer.
>
> Signed-off-by: brian m. carlson <sandals@crustytoothpaste.net>
> ---
>  builtin/checkout.c | 4 +---
>  1 file changed, 1 insertion(+), 3 deletions(-)

Thanks.

Show 15 quoted lines

> diff --git a/builtin/checkout.c b/builtin/checkout.c
> index e9d111bb83..62b5e371bc 100644
> --- a/builtin/checkout.c
> +++ b/builtin/checkout.c
> @@ -621,9 +621,7 @@ static int reset_tree(struct tree *tree, const struct checkout_opts *o,
>  	opts.src_index = &the_index;
>  	opts.dst_index = &the_index;
>  	init_checkout_metadata(&opts.meta, info->refname,
> -			       info->commit ? &info->commit->object.oid :
> -			       is_null_oid(&info->oid) ? &tree->object.oid :
> -			       &info->oid,
> +			       info->commit ? &info->commit->object.oid : &null_oid,
>  			       NULL);
>  	parse_tree(tree);
>  	init_tree_desc(&tree_desc, tree->buffer, tree->size);