Merge branch 'sp/send-email-validate-charset' into next

"git send-email" has learned to be a bit more careful when it
accepts charset to use from the end-user, to avoid 'y' (mistaken
'yes' when expecting a charset like 'UTF-8') and other nonsense.

* sp/send-email-validate-charset:
  send-email: validate charset name in 8bit encoding prompt

Author: gitster

git-send-email.perl

@@ -23,6 +23,7 @@
 use Git::LoadCPAN::Error qw(:try);
 use Git;
 use Git::I18N;
+use Encode qw(find_encoding);
 
 Getopt::Long::Configure qw/ pass_through /;
 
@@ -1051,9 +1052,27 @@ sub file_declares_8bit_cte {
 	foreach my $f (sort keys %broken_encoding) {
 		print "    $f\n";
 	}
-	$auto_8bit_encoding = ask(__("Which 8bit encoding should I declare [UTF-8]? "),
-				  valid_re => qr/.{4}/, confirm_only => 1,
-				  default => "UTF-8");
+	while (1) {
+		my $encoding = ask(
+			__("Declare which 8bit encoding to use [default: UTF-8]? "),
+			valid_re => qr/^\S+$/,
+			default  => "UTF-8");
+		next unless defined $encoding;
+		if (find_encoding($encoding)) {
+			$auto_8bit_encoding = $encoding;
+			last;
+		}
+		my $yesno = ask(
+			sprintf(
+			__("'%s' does not appear to be a valid charset name. Use it anyway [y/N]? "),
+			$encoding),
+			valid_re => qr/^(?:y|n)/i,
+			default => "n");
+		if (defined $yesno && $yesno =~ /^y/i) {
+			$auto_8bit_encoding = $encoding;
+			last;
+		}
+	}
 }
 
 if (!$force) {

t/t9001-send-email.sh

@@ -1691,7 +1691,7 @@ test_expect_success $PREREQ 'asks about and fixes 8bit encodings' '
 			email-using-8bit >stdout &&
 	grep "do not declare a Content-Transfer-Encoding" stdout &&
 	grep email-using-8bit stdout &&
-	grep "Which 8bit encoding" stdout &&
+	grep "Declare which 8bit encoding to use" stdout &&
 	grep -E "Content|MIME" msgtxt1 >actual &&
 	test_cmp content-type-decl actual
 '