2 files changed, 130 insertions, 25 deletions

diff --git a/cgit.css b/cgit.css
index 3f37165..9e6d2a4 100644
--- a/cgit.css
+++ b/cgit.css
@@ -626,8 +626,13 @@ table.ssdiff td.add_dark {
         background: #aca;
         min-width: 50%;
 }
 
+table.ssdiff span.add {
+        background: #cfc;
+        font-weight: bold;
+}
+
 table.ssdiff td.del {
         color: black;
         background: #fcc;
         min-width: 50%;
@@ -638,8 +643,13 @@ table.ssdiff td.del_dark {
         background: #caa;
         min-width: 50%;
 }
 
+table.ssdiff span.del {
+        background: #fcc;
+        font-weight: bold;
+}
+
 table.ssdiff td.changed {
         color: black;
         background: #ffc;
         min-width: 50%;
diff --git a/ui-ssdiff.c b/ui-ssdiff.c
index 5673642..408e620 100644
--- a/ui-ssdiff.c
+++ b/ui-ssdiff.c
@@ -14,8 +14,54 @@ struct deferred_lines {
 
 static struct deferred_lines *deferred_old, *deferred_old_last;
 static struct deferred_lines *deferred_new, *deferred_new_last;
 
+static char *longest_common_subsequence(char *A, char *B)
+{
+        int i, j, ri;
+        int m = strlen(A);
+        int n = strlen(B);
+        int L[m + 1][n + 1];
+        int tmp1, tmp2;
+        int lcs_length;
+        char *result;
+
+        for (i = m; i >= 0; i--) {
+                for (j = n; j >= 0; j--) {
+                        if (A[i] == '\0' || B[j] == '\0') {
+                                L[i][j] = 0;
+                        } else if (A[i] == B[j]) {
+                                L[i][j] = 1 + L[i + 1][j + 1];
+                        } else {
+                                tmp1 = L[i + 1][j];
+                                tmp2 = L[i][j + 1];
+                                L[i][j] = (tmp1 > tmp2 ? tmp1 : tmp2);
+                        }
+                }
+        }
+
+        lcs_length = L[0][0];
+        result = xmalloc(lcs_length + 2);
+        memset(result, 0, sizeof(*result) * (lcs_length + 2));
+
+        ri = 0;
+        i = 0;
+        j = 0;
+        while (i < m && j < n) {
+                if (A[i] == B[j]) {
+                        result[ri] = A[i];
+                        ri += 1;
+                        i += 1;
+                        j += 1;
+                } else if (L[i + 1][j] >= L[i][j + 1]) {
+                        i += 1;
+                } else {
+                        j += 1;
+                }
+        }
+        return result;
+}
+
 static int line_from_hunk(char *line, char type)
 {
         char *buf1, *buf2;
         int len;
@@ -72,8 +118,19 @@ static char *replace_tabs(char *line)
         }
         return result;
 }
 
+static int calc_deferred_lines(struct deferred_lines *start)
+{
+        struct deferred_lines *item = start;
+        int result = 0;
+        while (item) {
+                result += 1;
+                item = item->next;
+        }
+        return result;
+}
+
 static void deferred_old_add(char *line, int line_no)
 {
         struct deferred_lines *item = xmalloc(sizeof(struct deferred_lines));
         item->line = xstrdup(line);
@@ -100,53 +157,93 @@ static void deferred_new_add(char *line, int line_no)
                 deferred_new = deferred_new_last = item;
         }
 }
 
-static void print_ssdiff_line(char *class, int old_line_no, char *old_line,
-                              int new_line_no, char *new_line)
+static void print_part_with_lcs(char *class, char *line, char *lcs)
+{
+        int line_len = strlen(line);
+        int i, j;
+        char c[2] = " ";
+        int same = 1;
+
+        j = 0;
+        for (i = 0; i < line_len; i++) {
+                c[0] = line[i];
+                if (same) {
+                        if (line[i] == lcs[j])
+                                j += 1;
+                        else {
+                                same = 0;
+                                htmlf("<span class='%s'>", class);
+                        }
+                } else if (line[i] == lcs[j]) {
+                        same = 1;
+                        htmlf("</span>");
+                        j += 1;
+                }
+                html_txt(c);
+        }
+}
+
+static void print_ssdiff_line(char *class,
+                              int old_line_no,
+                              char *old_line,
+                              int new_line_no,
+                              char *new_line, int individual_chars)
 {
+        char *lcs = NULL;
+        if (old_line)
+                old_line = replace_tabs(old_line + 1);
+        if (new_line)
+                new_line = replace_tabs(new_line + 1);
+        if (individual_chars && old_line && new_line)
+                lcs = longest_common_subsequence(old_line, new_line);
         html("<tr>");
         if (old_line_no > 0)
                 htmlf("<td class='lineno'>%d</td><td class='%s'>",
                       old_line_no, class);
         else if (old_line)
                 htmlf("<td class='lineno'></td><td class='%s'>", class);
         else
                 htmlf("<td class='lineno'></td><td class='%s_dark'>", class);
-
         if (old_line) {
-                old_line = replace_tabs(old_line + 1);
-                html_txt(old_line);
-                free(old_line);
+                if (lcs)
+                        print_part_with_lcs("del", old_line, lcs);
+                else
+                        html_txt(old_line);
         }
 
         html("</td>");
-
         if (new_line_no > 0)
                 htmlf("<td class='lineno'>%d</td><td class='%s'>",
                       new_line_no, class);
         else if (new_line)
                 htmlf("<td class='lineno'></td><td class='%s'>", class);
         else
                 htmlf("<td class='lineno'></td><td class='%s_dark'>", class);
-
         if (new_line) {
-                new_line = replace_tabs(new_line + 1);
-                html_txt(new_line);
-                free(new_line);
+                if (lcs)
+                        print_part_with_lcs("add", new_line, lcs);
+                else
+                        html_txt(new_line);
         }
 
         html("</td></tr>");
+        if (lcs)
+                free(lcs);
+        if (new_line)
+                free(new_line);
+        if (old_line)
+                free(old_line);
 }
 
 static void print_deferred_old_lines()
 {
         struct deferred_lines *iter_old, *tmp;
-
         iter_old = deferred_old;
         while (iter_old) {
                 print_ssdiff_line("del", iter_old->line_no,
-                                  iter_old->line, -1, NULL);
+                                  iter_old->line, -1, NULL, 0);
                 tmp = iter_old->next;
                 free(iter_old);
                 iter_old = tmp;
         }
@@ -154,13 +251,12 @@ static void print_deferred_old_lines()
 
 static void print_deferred_new_lines()
 {
         struct deferred_lines *iter_new, *tmp;
-
         iter_new = deferred_new;
         while (iter_new) {
-                print_ssdiff_line("add", -1, NULL, iter_new->line_no,
-                                  iter_new->line);
+                print_ssdiff_line("add", -1, NULL,
+                                  iter_new->line_no, iter_new->line, 0);
                 tmp = iter_new->next;
                 free(iter_new);
                 iter_new = tmp;
         }
@@ -168,23 +264,26 @@ static void print_deferred_new_lines()
 
 static void print_deferred_changed_lines()
 {
         struct deferred_lines *iter_old, *iter_new, *tmp;
+        int n_old_lines = calc_deferred_lines(deferred_old);
+        int n_new_lines = calc_deferred_lines(deferred_new);
+        int individual_chars = (n_old_lines == n_new_lines ? 1 : 0);
 
         iter_old = deferred_old;
         iter_new = deferred_new;
         while (iter_old || iter_new) {
                 if (iter_old && iter_new)
                         print_ssdiff_line("changed", iter_old->line_no,
                                           iter_old->line,
-                                          iter_new->line_no, iter_new->line);
+                                          iter_new->line_no, iter_new->line,
+                                          individual_chars);
                 else if (iter_old)
                         print_ssdiff_line("changed", iter_old->line_no,
-                                          iter_old->line, -1, NULL);
+                                          iter_old->line, -1, NULL, 0);
                 else if (iter_new)
                         print_ssdiff_line("changed", -1, NULL,
-                                          iter_new->line_no, iter_new->line);
-
+                                          iter_new->line_no, iter_new->line, 0);
                 if (iter_old) {
                         tmp = iter_old->next;
                         free(iter_old);
                         iter_old = tmp;
@@ -201,16 +300,14 @@ static void print_deferred_changed_lines()
 void cgit_ssdiff_print_deferred_lines()
 {
         if (!deferred_old && !deferred_new)
                 return;
-
         if (deferred_old && !deferred_new)
                 print_deferred_old_lines();
         else if (!deferred_old && deferred_new)
                 print_deferred_new_lines();
         else
                 print_deferred_changed_lines();
-
         deferred_old = deferred_old_last = NULL;
         deferred_new = deferred_new_last = NULL;
 }
 
@@ -219,11 +316,9 @@ void cgit_ssdiff_print_deferred_lines()
  */
 void cgit_ssdiff_line_cb(char *line, int len)
 {
         char c = line[len - 1];
-
         line[len - 1] = '\0';
-
         if (line[0] == '@') {
                 current_old_line = line_from_hunk(line, '-');
                 current_new_line = line_from_hunk(line, '+');
         }
@@ -231,9 +326,9 @@ void cgit_ssdiff_line_cb(char *line, int len)
         if (line[0] == ' ') {
                 if (deferred_old || deferred_new)
                         cgit_ssdiff_print_deferred_lines();
                 print_ssdiff_line("ctx", current_old_line, line,
-                                  current_new_line, line);
+                                  current_new_line, line, 0);
                 current_old_line += 1;
                 current_new_line += 1;
         } else if (line[0] == '+') {
                 deferred_new_add(line, current_new_line);