lib/PublicInbox/LEI.pm         | 2 +-
 lib/PublicInbox/LeiMailDiff.pm | 6 +++---

diff --git a/lib/PublicInbox/LEI.pm b/lib/PublicInbox/LEI.pm
index f9d24f29c87d0dfc82056c8b767b64ca05c8a46b..96f7c5e315a9d4b8b182953cd0a6269db880ca66 100644
--- a/lib/PublicInbox/LEI.pm
+++ b/lib/PublicInbox/LEI.pm
@@ -202,7 +202,7 @@ 	@diff_opt, @lxs_opt, @net_opt, @c_opt ],
 
 'mail-diff' => [ '--stdin|LOCATION...', 'diff the contents of emails',
 	'stdin|', # /|\z/ must be first for lone dash
-	qw(verbose|v+ color:s no-color raw-header),
+	qw(verbose|v+ in-format|F=s color:s no-color raw-header),
 	@diff_opt, @net_opt, @c_opt ],
 
 'add-external' => [ 'LOCATION',
diff --git a/lib/PublicInbox/LeiMailDiff.pm b/lib/PublicInbox/LeiMailDiff.pm
index 4f3a4608d8e0beceafda3830b9fff41ffbae6b4d..b21a0c366fd68aa6c8198a99e7bbf5b7f9ea8cca 100644
--- a/lib/PublicInbox/LeiMailDiff.pm
+++ b/lib/PublicInbox/LeiMailDiff.pm
@@ -76,7 +76,7 @@ }
 
 sub lei_mail_diff {
 	my ($lei, @argv) = @_;
-	$lei->{opt}->{'in-format'} //= 'eml';
+	$lei->{opt}->{'in-format'} //= 'eml' if !grep(/\A[a-z0-9]+:/i, @argv);
 	my $self = bless {}, __PACKAGE__;
 	$self->prepare_inputs($lei, \@argv) or return;
 	my $isatty = -t $lei->{1};
@@ -94,7 +94,7 @@
 no warnings 'once';
 *net_merge_all_done = \&PublicInbox::LeiInput::input_only_net_merge_all_done;
 
-package PublicInbox::ContentDigestDbg;
+package PublicInbox::ContentDigestDbg; # cf. PublicInbox::ContentDigest
 use strict;
 use v5.10.1;
 use Data::Dumper;
@@ -103,7 +103,7 @@ sub new { bless { dig => Digest::SHA->new(256), fh => $_[1] }, __PACKAGE__ }
 
 sub add {
 	$_[0]->{dig}->add($_[1]);
-	print { $_[0]->{fh} } Dumper($_[1]) or die "print $!";
+	print { $_[0]->{fh} } Dumper([split(/^/sm, $_[1])]) or die "print $!";
 }
 
 sub hexdigest { $_[0]->{dig}->hexdigest; }