Subject: Re: [RFC] send-email: UTF-8 encoding in subject line

From: Shreyansh Paliwal <[email-masked]>
Date: Sun, 22 Feb 2026 21:22:01 +0530

> On Sun, Feb 22, 2026 at 9:07 AM Shreyansh Paliwal
> <[email-masked]> wrote:
> >
> > > > That makes sense, I tried it below.
> > > > I also wondered whether, in addition to this, it might be helpful to warn on
> > > > an invalid charset, and/or possibly fall back to UTF-8.
> > >
> > > Agreed on the first half of the statement, if we have an easy and
> > > portable way to tell if a given random string names a valid charset.
> > > I do not recommend to "fall back" to anything, if we are asking an
> > > input from the user.
> >
> > Following up on this, I tried adding a warning when the provided charset
> > does not appear to be valid. Current flow is,
> >
> >   Which 8bit encoding should I declare [UTF-8]? y
> >   Are you sure you want to use <y> [y/N]? y
> >
> > With the additional check, it becomes,
> >
> >   Which 8bit encoding should I declare [default: UTF-8]? y
> >   warning: 'y' does not appear to be a valid charset name.
> >   Are you sure you want to use <y> [y/N]?
> >
> > This uses find_encoding() from Perl’s Encode module to detect any
> > unrecognized charset names.
> >
> > Let me know what you think.
> > Also, is there any new test that should be added for this change?
> >
> > Signed-off-by: Shreyansh Paliwal <[email-masked]>
> > ---
> >  git-send-email.perl | 23 ++++++++++++++++++++---
> >  1 file changed, 20 insertions(+), 3 deletions(-)
> >
> > diff --git a/git-send-email.perl b/git-send-email.perl
> > index cd4b316ddc..e62fa259ba 100755
> > --- a/git-send-email.perl
> > +++ b/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 /;
> >
> > @@ -1044,9 +1045,25 @@ 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 $encoding = ask(__("Which 8bit encoding should I declare [default: UTF-8]? "),
> > +                       valid_re => qr/^\S+$/,
> > +                       default  => "UTF-8");
>
> Here we change things, right?
>
> - The original validation is "at least 4 characters", the new
> validation is "at least one non-blank." I'm not sure why we'd prefer
> one or the other, frankly. The original goes to 852a15d748
> (send-email: ask confirmation if given encoding name is very short,
> 2015-02-13), which is motivated by the same problem we're discussing
> here!

I see.
My understanding of the earlier change (852a15d748) is that the
length check was intended as a heuristic check to catch obviously invalid
inputs like "y" and trigger an extra confirmation based on the fact that
charset names would be at least 4 letters.

With the additional find_encoding() check, the validation becomes semantic
rather than length-based, recognized charset names are accepted directly,
while unrecognized ones trigger a warning and still require explicit
confirmation. The relaxed regex (at least one non-blank) is only meant to
ensure we receive some non-empty input before passing it to find_encoding().

> - We get rid of confirm_only, since we're about to roll our own
> confirmation below:
>
> > +               next unless defined $encoding;
> > +               if (find_encoding($encoding)) {
> > +                       $auto_8bit_encoding = $encoding;
> > +                       last;
> > +               }
> > +               printf STDERR __("warning: '%s' does not appear to be a valid charset name.\n"), $encoding;
> > +               my $yesno = ask(
> > +                       sprintf(__("Are you sure you want to use <%s> [y/N]? "), $encoding),
> > +                       valid_re => qr/^(?:y|n)/i,
> > +                       default  => 'n');
>
> …which might want refactored a bit so it can stay close to the original? idk.
>

Actually the flow needed to change slightly to insert the validity warning
before the final confirmation step. Since ask() handles confirmation internally
using confrim_only and is used in multiple places, it seemed simpler to keep the
additional confirmation local here rather than modifying ask() itself.

Let me know what you think.

Best,
Shreyansh