Re: [PATCH v11 08/10] convert: advise canonical UTF encoding names

[Junio C Hamano <gitster@pobox.com>]

lars.schneider@autodesk.com writes:

> From: Lars Schneider <larsxschneider@gmail.com>
>
> The canonical name of an UTF encoding has the format UTF, dash, number,
> and an optionally byte order in upper case (e.g. UTF-8 or UTF-16BE).
> Some iconv versions support alternative names without a dash or with
> lower case characters.
>
> To avoid problems between different iconv version always suggest the
> canonical UTF names in advise messages.
>
> Signed-off-by: Lars Schneider <larsxschneider@gmail.com>
> ---

I think it is probably better to squash this to earlier step,
i.e. jumping straight to the endgame solution.

> diff --git a/convert.c b/convert.c
> index b80d666a6b..9a3ae7cce1 100644
> --- a/convert.c
> +++ b/convert.c
> @@ -279,12 +279,20 @@ static int validate_encoding(const char *path, const char *enc,
>  				"BOM is prohibited in '%s' if encoded as %s");
>  			/*
>  			 * This advice is shown for UTF-??BE and UTF-??LE encodings.
> +			 * We cut off the last two characters of the encoding name
> +			 # to generate the encoding name suitable for BOMs.
>  			 */

I somehow thought that I saw "s/#/*/" in somebody's response during
the previous round?

>  			const char *advise_msg = _(
>  				"The file '%s' contains a byte order "
> -				"mark (BOM). Please use %.6s as "
> +				"mark (BOM). Please use UTF-%s as "
>  				"working-tree-encoding.");
> -			advise(advise_msg, path, enc);
> +			const char *stripped = "";
> +			char *upper = xstrdup_toupper(enc);
> +			upper[strlen(upper)-2] = '\0';
> +			if (!skip_prefix(upper, "UTF-", &stripped))
> +				skip_prefix(stripped, "UTF", &stripped);
> +			advise(advise_msg, path, stripped);
> +			free(upper);

If this codepath is ever entered with "enc" that does not begin with
"UTF" (e.g. "Shift_JIS", which is impossible in the current code,
but I'll talk about future-proofing here), then neither of these
skip_prefix will trigger, and then you'd end up suggesting to use
"UTF-" that is nonsense.  Perhaps initialize stripped to NULL and
force advise to segv to catch such a programmer error?