gitweb: Highlight interesting parts of diff

Reading diff output is sometimes very hard, even if it's colored,
especially if lines differ only in few characters.  This is often true
when a commit fixes a typo or renames some variables or functions.

This commit teaches gitweb to highlight characters that are different
between old and new line with a light green/red background.  This should
work in the similar manner as in Trac or GitHub.

The algorithm that compares lines is based on contrib/diff-highlight.
Basically, it works by determining common prefix/suffix of corresponding
lines and highlightning only the middle part of lines.  For more
information, see contrib/diff-highlight/README.

Combined diffs are not supported but a following commit will change it.

Since we need to pass esc_html()'ed or esc_html_hl_regions()'ed lines to
format_diff_lines(), so it was taught to accept preformatted lines
passed as a reference.

Signed-off-by: Michał Kiedrowicz <michal.kiedrowicz@gmail.com>
Acked-by: Jakub Narębski <jnareb@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

1 files changed, 8 insertions, 0 deletions

diff --git a/gitweb/static/gitweb.css b/gitweb/static/gitweb.css
index c530355a7c..cb86d2d029 100644
--- a/gitweb/static/gitweb.css
+++ b/gitweb/static/gitweb.css
@@ -438,6 +438,10 @@ div.diff.add {
 	color: #008800;
 }
 
+div.diff.add span.marked {
+	background-color: #aaffaa;
+}
+
 div.diff.from_file a.path,
 div.diff.from_file {
 	color: #aa0000;
@@ -447,6 +451,10 @@ div.diff.rem {
 	color: #cc0000;
 }
 
+div.diff.rem span.marked {
+	background-color: #ffaaaa;
+}
+
 div.diff.chunk_header a,
 div.diff.chunk_header {
 	color: #990099;