Re: [PATCH v7] tracking branches: add advice to ambiguous refspec error

[Glen Choo <chooglen@google.com>]

"Tao Klerks via GitGitGadget" <gitgitgadget@gmail.com> writes:

> diff --git a/branch.c b/branch.c
> index 6b31df539a5..182f1c5a556 100644
> --- a/branch.c
> +++ b/branch.c
> @@ -18,17 +18,31 @@ struct tracking {
>  	int matches;
>  };
>  
> +struct find_tracked_branch_cb {
> +	struct tracking *tracking;
> +	struct string_list ambiguous_remotes;
> +};
> +
>  static int find_tracked_branch(struct remote *remote, void *priv)
>  {
> -	struct tracking *tracking = priv;
> +	struct find_tracked_branch_cb *ftb = priv;
> +	struct tracking *tracking = ftb->tracking;
>  
>  	if (!remote_find_tracking(remote, &tracking->spec)) {
> -		if (++tracking->matches == 1) {
> +		switch (++tracking->matches) {
> +		case 1:
>  			string_list_append(tracking->srcs, tracking->spec.src);
>  			tracking->remote = remote->name;
> -		} else {
> +			break;
> +		case 2:
> +			/* there are at least two remotes; backfill the first one */
> +			string_list_append(&ftb->ambiguous_remotes, tracking->remote);
> +			/* fall through */
> +		default:
> +			string_list_append(&ftb->ambiguous_remotes, remote->name);
>  			free(tracking->spec.src);
>  			string_list_clear(tracking->srcs, 0);
> +		break;
>  		}
>  		tracking->spec.src = NULL;
>  	}

Ah I see, on the first iteration, we set the first remote's name to
tracking->remote, and on the second iteration, we copy that value to the
list before copying the _current_ remote's name to the list.

> -test_expect_success 'avoid ambiguous track' '
> +test_expect_success 'avoid ambiguous track and advise' '
>  	git config branch.autosetupmerge true &&
>  	git config remote.ambi1.url lalala &&
>  	git config remote.ambi1.fetch refs/heads/lalala:refs/heads/main &&
>  	git config remote.ambi2.url lilili &&
>  	git config remote.ambi2.fetch refs/heads/lilili:refs/heads/main &&
> -	test_must_fail git branch all1 main &&
> +	cat <<-EOF >expected &&
> +	fatal: not tracking: ambiguous information for ref '\''refs/heads/main'\''
> +	hint: There are multiple remotes whose fetch refspecs map to the remote
> +	hint: tracking ref '\''refs/heads/main'\'':
> +	hint:   ambi1
> +	hint:   ambi2
> +	hint: ''
> +	hint: This is typically a configuration error.
> +	hint: ''
> +	hint: To support setting up tracking branches, ensure that
> +	hint: different remotes'\'' fetch refspecs map into different
> +	hint: tracking namespaces.
> +	EOF
> +	test_must_fail git branch all1 main 2>actual &&
> +	test_cmp expected actual &&
>  	test -z "$(git config branch.all1.merge)"
>  '

And this test shows that this indeed does what we think it does. Nicely
done.

I notice that we there is an instance of test -z "$(some git command)",
which IIRC is discouraged because it would mask a failure in the git
command, but that's not new and I don't think it needs to be fixed in
this series anyway.

Reviewed-by: Glen Choo <chooglen@google.com>