Subject: Re: [PATCH v2 09/14] reset_head(): make default_reflog_action optional

From: Junio C Hamano <[email-masked]>
Date: Thu, 09 Dec 2021 11:23:41 -0800

"Phillip Wood via GitGitGadget" <[email-masked]> writes:

> From: Phillip Wood <[email-masked]>
>
> This parameter is only needed when a ref is going to be updated and
> the caller does not pass an explicit reflog message. Callers that are
> only discarding uncommitted changes in the working tree such as such
> as "rebase --skip" or create_autostash() do not update any refs so
> should not have to worry about passing this parameter.

This answers the question I had on 07/14.  I think the part with
create_autostash() in this step should be dropped, and 07/14 should
be done after this step.

Unlike "", NULL makes it very clear that it will be a bug if the
implementation used it as the message.

> This change is not intended to have any user visible changes. The
> pointer comparison between `oid` and `&head_oid` checks that the
> caller did not pass an oid to be checked out. As no callers pass
> RESET_HEAD_RUN_POST_CHECKOUT_HOOK without passing an oid there are
> no changes to when the post-checkout hook is run. As update_ref() only
> updates the ref if the oid passed to it differs from the current ref
> there are no changes to when HEAD is updated.
>
> Signed-off-by: Phillip Wood <[email-masked]>
> ---
>  builtin/rebase.c | 10 ++++------
>  reset.c          | 16 ++++++++++++----
>  sequencer.c      |  2 +-
>  3 files changed, 17 insertions(+), 11 deletions(-)
>
> diff --git a/builtin/rebase.c b/builtin/rebase.c
> index 832e6954827..3d78b5c8bef 100644
> --- a/builtin/rebase.c
> +++ b/builtin/rebase.c
> @@ -585,8 +585,7 @@ static int move_to_original_branch(struct rebase_options *opts)
>  		    opts->head_name);
>  	ret = reset_head(the_repository, NULL, opts->head_name,
>  			 RESET_HEAD_REFS_ONLY,
> -			 orig_head_reflog.buf, head_reflog.buf,
> -			 DEFAULT_REFLOG_ACTION);
> +			 orig_head_reflog.buf, head_reflog.buf, NULL);
>  
>  	strbuf_release(&orig_head_reflog);
>  	strbuf_release(&head_reflog);
> @@ -822,7 +821,7 @@ static int checkout_up_to_date(struct rebase_options *options)
>  		    options->switch_to);
>  	if (reset_head(the_repository, &options->orig_head,
>  		       options->head_name, RESET_HEAD_RUN_POST_CHECKOUT_HOOK,
> -		       NULL, buf.buf, DEFAULT_REFLOG_ACTION) < 0)
> +		       NULL, buf.buf, NULL) < 0)
>  		ret = error(_("could not switch to %s"), options->switch_to);
>  	strbuf_release(&buf);
>  
> @@ -1273,7 +1272,7 @@ int cmd_rebase(int argc, const char **argv, const char *prefix)
>  		string_list_clear(&merge_rr, 1);
>  
>  		if (reset_head(the_repository, NULL, NULL, RESET_HEAD_HARD,
> -			       NULL, NULL, DEFAULT_REFLOG_ACTION) < 0)
> +			       NULL, NULL, NULL) < 0)
>  			die(_("could not discard worktree changes"));
>  		remove_branch_state(the_repository, 0);
>  		if (read_basic_state(&options))
> @@ -1778,8 +1777,7 @@ int cmd_rebase(int argc, const char **argv, const char *prefix)
>  			options.head_name ? options.head_name : "detached HEAD",
>  			oid_to_hex(&options.onto->object.oid));
>  		reset_head(the_repository, NULL, options.head_name,
> -			   RESET_HEAD_REFS_ONLY, "HEAD", msg.buf,
> -			   DEFAULT_REFLOG_ACTION);
> +			   RESET_HEAD_REFS_ONLY, "HEAD", msg.buf, NULL);
>  		strbuf_release(&msg);
>  		ret = finish_rebase(&options);
>  		goto cleanup;
> diff --git a/reset.c b/reset.c
> index 56d6e2a06d9..4a92e4bc30b 100644
> --- a/reset.c
> +++ b/reset.c
> @@ -22,8 +22,13 @@ static int update_refs(const struct object_id *oid, const char *switch_to_branch
>  	size_t prefix_len;
>  	int ret;
>  
> -	reflog_action = getenv(GIT_REFLOG_ACTION_ENVIRONMENT);
> -	strbuf_addf(&msg, "%s: ", reflog_action ? reflog_action : default_reflog_action);
> +	if ((update_orig_head && !reflog_orig_head) || !reflog_head) {
> +		if (!default_reflog_action)
> +			BUG("default_reflog_action must be given when reflog messages are omitted");
> +		reflog_action = getenv(GIT_REFLOG_ACTION_ENVIRONMENT);
> +		strbuf_addf(&msg, "%s: ", reflog_action ? reflog_action :
> +							  default_reflog_action);
> +	}
>  	prefix_len = msg.len;
>  
>  	if (update_orig_head) {
> @@ -71,6 +76,7 @@ int reset_head(struct repository *r, struct object_id *oid,
>  {
>  	unsigned reset_hard = flags & RESET_HEAD_HARD;
>  	unsigned refs_only = flags & RESET_HEAD_REFS_ONLY;
> +	unsigned update_orig_head = flags & RESET_ORIG_HEAD;
>  	struct object_id *head = NULL, head_oid;
>  	struct tree_desc desc[2] = { { NULL }, { NULL } };
>  	struct lock_file lock = LOCK_INIT;
> @@ -144,8 +150,10 @@ int reset_head(struct repository *r, struct object_id *oid,
>  		goto leave_reset_head;
>  	}
>  
> -	ret = update_refs(oid, switch_to_branch, head, reflog_head,
> -			  reflog_orig_head, default_reflog_action, flags);
> +	if (oid != &head_oid || update_orig_head || switch_to_branch)
> +		ret = update_refs(oid, switch_to_branch, head, reflog_head,
> +				  reflog_orig_head, default_reflog_action,
> +				  flags);
>  
>  leave_reset_head:
>  	rollback_lock_file(&lock);
> diff --git a/sequencer.c b/sequencer.c
> index 5c65f5f1ac5..78d203dec47 100644
> --- a/sequencer.c
> +++ b/sequencer.c
> @@ -4131,7 +4131,7 @@ void create_autostash(struct repository *r, const char *path)
>  		write_file(path, "%s", oid_to_hex(&oid));
>  		printf(_("Created autostash: %s\n"), buf.buf);
>  		if (reset_head(r, NULL, NULL, RESET_HEAD_HARD, NULL, NULL,
> -			       "") < 0)
> +			       NULL) < 0)
>  			die(_("could not reset --hard"));
>  
>  		if (discard_index(r->index) < 0 ||