dpkg-genchanges, dpkg-source: only split Binary field when it's too long

Applying the substitution on short lines will split them too even though
they are not longer than 980 chars.

scripts/dpkg-genchanges.pl

@@ -447,8 +447,10 @@ if (!defined($fields->{'Date'})) {
 }
 
 $fields->{'Binary'} = join(' ', map { $_->{'Package'} } $control->get_packages());
-# Avoid overly long line (>~1000 chars) by splitting over multiple lines
-$fields->{'Binary'} =~ s/(.{0,980}) /$1\n/g;
+# Avoid overly long line by splitting over multiple lines
+if (length($fields->{'Binary'}) > 980) {
+    $fields->{'Binary'} =~ s/(.{0,980}) /$1\n/g;
+}
 
 unshift(@archvalues,'source') unless is_binaryonly;
 @archvalues = ('all') if $include == ARCH_INDEP;

scripts/dpkg-source.pl

@@ -287,8 +287,10 @@ if ($options{'opmode'} =~ /^(-b|--print-format)$/) {
     }
     
     $fields->{'Binary'} = join(', ', @binarypackages);
-    # Avoid overly long line (>~1000 chars) by splitting over multiple lines
-    $fields->{'Binary'} =~ s/(.{0,980}), ?/$1,\n/g;
+    # Avoid overly long line by splitting over multiple lines
+    if (length($fields->{'Binary'}) > 980) {
+	$fields->{'Binary'} =~ s/(.{0,980}), ?/$1,\n/g;
+    }
 
     # Generate list of formats to try
     my @try_formats = (@cmdline_formats);