common-mark: small fixes

Down to 446 failed tests.

Fixed attribute names for HTML.
Fixed regexp for unquoted parts in HTML.
Added beginning of image link handling.
Fixed regexp for single backquote code.

t/common-markdown.t

@@ -0,0 +1,49 @@
+#!/usr/bin/env perl
+# Copyright (C) 2018  Alex Schroeder <alex@gnu.org>
+#
+# This program is free software; you can redistribute it and/or modify
+# it under the terms of the GNU General Public License as published by
+# the Free Software Foundation; either version 3 of the License, or
+# (at your option) any later version.
+#
+# This program is distributed in the hope that it will be useful,
+# but WITHOUT ANY WARRANTY; without even the implied warranty of
+# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+# GNU General Public License for more details.
+#
+# You should have received a copy of the GNU General Public License
+# along with this program.  If not, see <http://www.gnu.org/licenses/>.
+
+require './t/test.pl';
+package OddMuse;
+use Test::More;
+use JSON;
+use utf8;
+
+add_module('common-markdown.pl');
+
+sub load_tests {
+  my $spec = "t/common-markdown-spec-0.28.json";
+  open(my $fh, "<", $spec)
+      or die "Cannot open $spec: $!";
+  local $/ = undef;
+  return decode_json <$fh>;
+}
+
+sub normalize {
+  my $html = shift;
+  $html =~ s/\n$//s;
+  return $html;
+}
+
+my $tests = load_tests();
+
+for my $test (@$tests) {
+  my $name = $test->{example} . ". (" . $test->{section} . ")";
+  my $input = $test->{markdown};
+  my $output = apply_rules($input, 'p');
+  my $correct = normalize($test->{html});
+  is($output, $correct, $name);
+}
+
+done_testing();

t/test.pl

@@ -146,13 +146,11 @@ sub run_tests_negative {
 }
 
 sub apply_rules {
-  my $input = shift;
-  local *STDOUT;
-  $output = '';
-  open(STDOUT, '>', \$output) or die "Can't open memory file: $!";
-  $FootnoteNumber = 0;
-  ApplyRules(QuoteHtml($input), 1);
-  return $output;
+  return ToString(sub {
+    my $input = shift;
+    $FootnoteNumber = 0;
+    ApplyRules(QuoteHtml($input), 1, undef, undef, @_);
+  }, @_);
 }
 
 # alternating input and output strings for applying macros instead of rules