repobrowse: italicize removed lines in diffs

This doesn't look too horrible on displays which render italics
and even degrades gracefully in text-only displays to underline
or colors in other terminals (lynx).  Do not italicize leading
whitespace, since the fallback to underlines looks too noisy.

1 files changed, 34 insertions, 8 deletions

diff --git a/lib/PublicInbox/RepobrowseGitCommit.pm b/lib/PublicInbox/RepobrowseGitCommit.pm
index 64d0b607..b5ffb2bf 100644
--- a/lib/PublicInbox/RepobrowseGitCommit.pm
+++ b/lib/PublicInbox/RepobrowseGitCommit.pm
@@ -82,7 +82,7 @@ sub git_commit_stream {
         local $/ = "\n";
         my $cmt = '[a-f0-9]+';
         my $diff = { h => $h, p => \@p, rel => $rel };
-        my $cc_add;
+        my ($cc_ins, $cc_del);
         while (defined($l = <$log>)) {
                 if ($help) {
                         $fh->write($help);
@@ -96,11 +96,16 @@ sub git_commit_stream {
                         $l = git_diff_ab_index($diff, $1, $2, $3) . "\n";
                 } elsif ($l =~ /^@@ (\S+) (\S+) @@(.*)$/) { # regular
                         $l = git_diff_ab_hunk($diff, $1, $2, $3) . "\n";
-                } elsif ($l =~ /^\+/ || ($cc_add && $l =~ $cc_add)) {
-                        $l = git_diff_add($l) . "\n";
+
+                } elsif ($l =~ /^\+{1,3}\s*/ || ($cc_ins && $l =~ $cc_ins)) {
+                        $l = git_diff_ins($l) . "\n";
+                } elsif ($l =~ s/^(\-{1,3}\s*)// ||
+                                        ($cc_del && $l =~ s/$cc_del//)) {
+                        $l = git_diff_del($1, $l) . "\n";
                 } elsif ($l =~ /^index ($cmt,[^\.]+)\.\.($cmt)(.*)$/o) { # --cc
                         $l = git_diff_cc_index($diff, $1, $2, $3) . "\n";
-                        $cc_add ||= $diff->{cc_add};
+                        $cc_ins ||= $diff->{cc_ins};
+                        $cc_del ||= $diff->{cc_del};
                 } elsif ($l =~ /^(@@@+) (\S+.*\S+) @@@+(.*)$/) { # --cc
                         $l = git_diff_cc_hunk($diff, $1, $2, $3) . "\n";
                 } else {
@@ -278,10 +283,11 @@ sub git_diff_cc_index {
         $end = utf8_html($end);
         my @before = split(',', $before);
         $diff->{pobj_cc} = \@before;
-        $diff->{cc_add} ||= eval {
+        unless ($diff->{cc_ins}) {
                 my $n = scalar(@before) - 1;
-                qr/^ {0,$n}[\+]/;
-        };
+                $diff->{cc_ins} = qr/^ {0,$n}[\+]\s*/;
+                $diff->{cc_del} = qr/^( {0,$n}[\-]\s*)/;
+        }
 
         # not wasting bandwidth on links here, yet
         # links in hunk headers are far more useful with line offsets
@@ -346,12 +352,32 @@ sub git_diffstat_rename {
         @base ? "$base/{$from =&gt; $to}" : "$from =&gt; $to";
 }
 
-sub git_diff_add {
+# It would be nice to be able to use colors for showing diff hunks.
+# Unfortunately, the default green+red colors in common web viewers
+# (gitweb, cgit, etc) are difficult to read for some people, myself
+# included.
+#
+# We cannot rely on CSS styling since it is unsafe and incompatible with
+# some browsers.
+#
+# Tried using semantic tags (ins and del).  Unfortunately, alignment
+# gets completely screwed in text-only browsers.  On common GUI browsers,
+# <del> renders unreadably by default (strike-throughs) and <ins> is
+# visually too noisy (with underlines).  So we'll bold added lines and
+# leave deleted lines alone (prefixed with '-')
+sub git_diff_ins {
         my ($l) = @_;
         chomp $l;
         '<b>'.utf8_html($l).'</b>';
 }
 
+sub git_diff_del {
+        my ($pfx, $l) = @_;
+        chomp $l;
+        # underline fallbacks look ugly with leading whitespace
+        $pfx. '<i>'.utf8_html($l).'</i>';
+}
+
 sub git_parent_line {
         my ($pfx, $p, $q, $git, $rel, $path) = @_;
         my $qs = $q->qs(id => $p);