Subject: Re: [PATCH v3] blame: prevent error if range ends past end of file

From: Junio C Hamano <[email-masked]>
Date: Fri, 27 Oct 2017 10:58:34 +0900

Isabella Stephens <[email-masked]> writes:

> diff --git a/builtin/blame.c b/builtin/blame.c
> index 67adaef4d..b5b9db147 100644
> --- a/builtin/blame.c
> +++ b/builtin/blame.c
> @@ -878,13 +878,13 @@ int cmd_blame(int argc, const char **argv, const char *prefix)
>  				    nth_line_cb, &sb, lno, anchor,
>  				    &bottom, &top, sb.path))
>  			usage(blame_usage);
> -		if (lno < top || ((lno || bottom) && lno < bottom))
> +		if ((lno || bottom) && lno < bottom)
>  			die(Q_("file %s has only %lu line",
>  			       "file %s has only %lu lines",
>  			       lno), path, lno);
>  		if (bottom < 1)
>  			bottom = 1;
> -		if (top < 1)
> +		if (top < 1 || lno < top)
>  			top = lno;

This section sanity-checks first and then tweaks the values it
allowed to pass the check.  Because it wants to later fix up an
overly large "top" by capping to "lno" (i.e. total line number), the
patch needs to loosen the early sanity-check.  And the "fixed up"
values are never checked if they are sane.

For example, with an empty file (i.e. lno == 0), you can ask "git
blame -L1,-4 ("i.e. "at most four lines, ending at line #1") and the
code silently accepts the input without noticing that the request is
an utter nonsense; "file X has only 0 lines" error is given a chance
to kick in.

There should be an "is the range sensible?" check after all the
tweaking to bottom and top are done, I think.

>  		bottom--;
>  		range_set_append_unsafe(&ranges, bottom, top);
> diff --git a/t/t8003-blame-corner-cases.sh b/t/t8003-blame-corner-cases.sh
> index 661f9d430..728209fa3 100755
> --- a/t/t8003-blame-corner-cases.sh
> +++ b/t/t8003-blame-corner-cases.sh
> @@ -216,14 +216,13 @@ test_expect_success 'blame -L with invalid start' '
>  '
>  
>  test_expect_success 'blame -L with invalid end' '
> -	test_must_fail git blame -L1,5 tres 2>errors &&
> -	test_i18ngrep "has only 2 lines" errors
> +	git blame -L1,5 tres >out &&
> +	test_line_count = 2 out
>  '
>  
>  test_expect_success 'blame parses <end> part of -L' '
>  	git blame -L1,1 tres >out &&
> -	cat out &&
> -	test $(wc -l < out) -eq 1
> +	test_line_count = 1 out
>  '
>  
>  test_expect_success 'indent of line numbers, nine lines' '