Re: [PATCH] format-patch: notice failure to open cover letter for writing

[Jeff King <peff@peff.net>]

On Thu, Feb 21, 2019 at 03:50:11PM -0800, Junio C Hamano wrote:

> The make_cover_letter() function is supposed to open a new file for
> writing, and let the caller write into it via FILE *rev->diffopt.file
> but because the function does not return anything, the caller does not
> bother checking the return value.
> 
> Make sure it dies, instead of keep going with a NULL output
> filestream and relying on it to cause a crash.

Definitely makes sense.

> diff --git a/builtin/log.c b/builtin/log.c
> index 3e145fe502..43fc9a07df 100644
> --- a/builtin/log.c
> +++ b/builtin/log.c
> @@ -1047,7 +1047,7 @@ static void make_cover_letter(struct rev_info *rev, int use_stdout,
>  
>  	if (!use_stdout &&
>  	    open_next_file(NULL, rev->numbered_files ? NULL : "cover-letter", rev, quiet))
> -		return;
> +		die(_("Failed to create cover-letter file"));

I wondered if we should be showing errno here, but it looks like
open_next_file() will give us a more specific error (including errno if
applicable).

I'd suggest s/F/f/ in the message to match our usual style, though I see
this code has a lot of capitalized errors already. :)

> +test_expect_success 'failure to write cover-letter aborts gracefully' '
> +	test_when_finished "rmdir 0000-cover-letter.patch" &&
> +	mkdir 0000-cover-letter.patch &&
> +	test_must_fail git format-patch --no-renames --cover-letter -1
> +'

Cute test. :)

-Peff