Subject: Re: [PATCH v4 4/8] fetch: fix missing from-reference when fetching HEAD:foo

From: Junio C Hamano <[email-masked]>
Date: Tue, 09 May 2023 12:28:16 -0700

Patrick Steinhardt <[email-masked]> writes:

> But it is not intended when displaying the updated references and would
> cause us to miss the left-hand side of the displayed reference update:
>
> ```
> $ git fetch origin HEAD:foo
> From https://github.com/git/git
>  * [new ref]                          -> foo
> ```
> The HEAD string is clearly missing from the left-hand side of the arrow,
> which is further stressed by the point that the following commands show
> the left-hand side as expected:
>
> ```
> $ git fetch origin HEAD
> From https://github.com/git/git
>  * branch                  HEAD       -> FETCH_HEAD

I do not mind being explicit and showing HEAD in this case for the
sake of consistency.

But speaking for the past developers, it was deliberate to omit what
is common from the output to make it more terse, IIRC, and I think
it is unfair to call it a "BUG".

Back when we wrote git-fetch-script, the output was a lot more
verbose, and through efforts like 165f3902 (git-fetch: more terse
fetch output, 2007-11-03) and numerous others over time, we got to
the current output.

> Note that this patch also changes formatting of the block that computes
> the "kind" and "what" variables. This is done on purpose so that it is
> part of the diff, hopefully making the change easier to comprehend.

Just to help readers, "kind" is the category like branch, tag,
etc. and "what" is the concrete name like 'master' and 'foo'.

> diff --git a/builtin/fetch.c b/builtin/fetch.c
> index 08d7fc7233..6aecf549e8 100644
> --- a/builtin/fetch.c
> +++ b/builtin/fetch.c
> @@ -918,12 +918,14 @@ static void display_ref_update(struct display_state *display_state, char code,
>  	}
>  
>  	width = (summary_width + strlen(summary) - gettext_width(summary));
> +	remote = prettify_refname(remote);
> +	local = prettify_refname(local);
>  
>  	strbuf_addf(&display_state->buf, " %c %-*s ", code, width, summary);
>  	if (!display_state->compact_format)
> -		print_remote_to_local(display_state, remote, prettify_refname(local));
> +		print_remote_to_local(display_state, remote, local);
>  	else
> -		print_compact(display_state, remote, prettify_refname(local));
> +		print_compact(display_state, remote, local);
>  	if (error)
>  		strbuf_addf(&display_state->buf, "  (%s)", error);
>  	strbuf_addch(&display_state->buf, '\n');
> @@ -934,7 +936,7 @@ static void display_ref_update(struct display_state *display_state, char code,
>  static int update_local_ref(struct ref *ref,
>  			    struct ref_transaction *transaction,
>  			    struct display_state *display_state,
> -			    const char *remote, const struct ref *remote_ref,
> +			    const struct ref *remote_ref,
>  			    int summary_width)
>  {
>  	struct commit *current = NULL, *updated;
> @@ -946,7 +948,7 @@ static int update_local_ref(struct ref *ref,
>  	if (oideq(&ref->old_oid, &ref->new_oid)) {
>  		if (verbosity > 0)
>  			display_ref_update(display_state, '=', _("[up to date]"), NULL,
> -					   remote, ref->name, summary_width);
> +					   remote_ref->name, ref->name, summary_width);

Makes sense.  The variable "remote" (now removed) holds what to
write to FETCH_HEAD to be used to formulate a merge message by the
caller, but this function is purely to report the ref updates and
has no need to have access to that information.

> @@ -1252,14 +1254,13 @@ static int store_updated_refs(struct display_state *display_state,
>  			if (!strcmp(rm->name, "HEAD")) {
>  				kind = "";
>  				what = "";
> -			}
> -			else if (skip_prefix(rm->name, "refs/heads/", &what))
> +			} else if (skip_prefix(rm->name, "refs/heads/", &what)) {
>  				kind = "branch";
> -			else if (skip_prefix(rm->name, "refs/tags/", &what))
> +			} else if (skip_prefix(rm->name, "refs/tags/", &what)) {
>  				kind = "tag";
> -			else if (skip_prefix(rm->name, "refs/remotes/", &what))
> +			} else if (skip_prefix(rm->name, "refs/remotes/", &what)) {
>  				kind = "remote-tracking branch";
> -			else {
> +			} else {
>  				kind = "";
>  				what = rm->name;
>  			}

This is a bit noisier than necessary.  It took me a while until I
realized that this hunk is a no-op.

> @@ -1277,7 +1278,7 @@ static int store_updated_refs(struct display_state *display_state,
>  					  display_state->url_len);
>  
>  			if (ref) {
> -				rc |= update_local_ref(ref, transaction, display_state, what,
> +				rc |= update_local_ref(ref, transaction, display_state,
>  						       rm, summary_width);
>  				free(ref);

Good.

> @@ -1288,7 +1289,7 @@ static int store_updated_refs(struct display_state *display_state,
>  				 */
>  				display_ref_update(display_state, '*',
>  						   *kind ? kind : "branch", NULL,
> -						   *what ? what : "HEAD",
> +						   rm->name,
>  						   "FETCH_HEAD", summary_width);

Good, too.  The original cleared "what" and then to compensate for
that had a logic to turn it back to "HEAD", but that is all gone by
passing rm->name down.  

I think we could pass "rm" and leave it to display_ref_update() what
string to use, if we wanted to further refine the output later.

Then somebody in the future may even want to see "HEAD" to be shown
as an empty string and that can all be done in display_ref_update().
It would fix the inconsistency that "git fetch origin HEAD" reports
"HEAD -> FETCH_HEAD" by hiding "HEAD" just like the case where
fetching "HEAD:foo" does, going in the other direction, I would
think.

Thanks.