Subject: Re: [PATCH 2/2] checkout-index: omit entries with no tempname from --temp output

From: Junio C Hamano <[email-masked]>
Date: Tue, 09 Feb 2021 13:35:36 -0800

Matheus Tavares <[email-masked]> writes:

> With --temp (or --stage=all, which implies --temp), checkout-index
> writes a list to stdout associating temporary file names to the entries'
> names. But if it fails to write an entry, and the failure happens before
> even assigning a temporary filename to that entry, we get an odd output
> line. This can be seen when trying to check out a symlink whose blob is
> missing:
>
> $ missing_blob=$(git hash-object --stdin </dev/null)
> $ git update-index --add --cacheinfo 120000,$missing_blob,foo
> $ git checkout-index --temp foo
> error: unable to read sha1 file of foo (e69de29bb2d1d6434b8b29ae775ad8c2e48c5391)
>         foo
>
> The 'TAB foo' line is not much useful and it might break scripts that
> expect the 'tempname TAB foo' output. So let's omit such entries from
> the stdout list (but leaving the error message on stderr).

Makes quite a lot of sense.

>  	if (CHECKOUT_ALL == checkout_stage) {
> -		for (i = 1; i < 4; i++) {
> -			if (i > 1)
> -				putchar(' ');
> -			if (topath[i][0])
> -				fputs(topath[i], stdout);
> -			else
> -				putchar('.');
> +		for (i = 1; i < 4; i++)
> +			if (topath[i][0]) {
> +				have_tempname = 1;
> +				break;
> +			}
> +
> +		if (have_tempname) {
> +			for (i = 1; i < 4; i++) {
> +				if (i > 1)
> +					putchar(' ');
> +				if (topath[i][0])
> +					fputs(topath[i], stdout);
> +				else
> +					putchar('.');
> +			}
>  		}
> -	} else
> +	} else if (topath[checkout_stage][0]) {
> +		have_tempname = 1;
>  		fputs(topath[checkout_stage], stdout);
> +	}
>  
> -	putchar('\t');
> -	write_name_quoted_relative(name, prefix, stdout,
> -				   nul_term_line ? '\0' : '\n');
> +	if (have_tempname) {
> +		putchar('\t');
> +		write_name_quoted_relative(name, prefix, stdout,
> +					   nul_term_line ? '\0' : '\n');
>  
> -	for (i = 0; i < 4; i++) {
> -		topath[i][0] = 0;
> +		for (i = 0; i < 4; i++) {
> +			topath[i][0] = 0;
> +		}
>  	}

Hmph, is topath[][] array used after this function gets called and
in what way?  Whether have_tempname is true or not, wouldn't we want
to clear it?

Thanks.