Re: [PATCH v10 7/9] convert: check for detectable errors in UTF encodings

Lars Schneider [off-list ref] writes:

I would like to advise the dashed form as this seems to be the
canonical form and it avoids cross platform issues. My macOS
iconv does not support the form without dashes.

Sure, that is why I said canonicalization without inserting dash
does not make much sense, hence an interim step with only upcasing
is not a good idea.  A possible interim solution would be to do
nothing (no dash insertion, no upcasing) and fixing both in a later
follow-up patch, but as I said, I do not care too strongly either
way.

Would this approach work for you?

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

Are you now interested in not having any interim step and jump
directly to the endgame solution?  If so, that is fine by me, too,
but as I already said earlier (i.e. not doing this BOM check for an
encoding that is not spelled in your canonical upcase-with-dash form
might be a feature that leaves an escape hatch), I am not all that
interested in enforcing policy at this point in the codepath to
begin with, so...