ui-log: Implement support for commit graphs

Teach CGit to print an ASCII art commit graph to the left of the commit
message, similar to 'git log --graph'. The graph adds extra lines (table
rows) to the log when needed to add/remove/shuffle edges in the graph.

When 'showmsg' is enabled, the graph is automatically padded to account
for the extra lines added by the commit message/notes.

This feature is controlled by a new config variable: "enable-commit-graph"
(disabled by default), and individual repos can control it by setting
"repo.enable-commit-graph".

Signed-off-by: Johan Herland <johan@herland.net>
Signed-off-by: Lars Hjemli <hjemli@gmail.com>

1 files changed, 82 insertions, 21 deletions

diff --git a/ui-log.c b/ui-log.c
index 6d7fcae..0d86fd5 100644
--- a/ui-log.c
+++ b/ui-log.c
@@ -72,32 +72,60 @@ void show_commit_decorations(struct commit *commit)
                         cgit_commit_link(buf, NULL, "deco", ctx.qry.head,
                                          sha1_to_hex(commit->object.sha1),
                                          ctx.qry.vpath, 0);
                 }
                 deco = deco->next;
         }
 }
 
-void print_commit(struct commit *commit)
+void print_commit(struct commit *commit, struct rev_info *revs)
 {
         struct commitinfo *info;
         char *tmp;
         int cols = 2;
+        struct strbuf graphbuf = STRBUF_INIT;
+
+        if (ctx.repo->enable_log_filecount) {
+                cols++;
+                if (ctx.repo->enable_log_linecount)
+                        cols++;
+        }
+
+        if (revs->graph) {
+                /* Advance graph until current commit */
+                while (!graph_next_line(revs->graph, &graphbuf)) {
+                        /* Print graph segment in otherwise empty table row */
+                        html("<tr class='nohover'><td/><td class='commitgraph'>");
+                        html(graphbuf.buf);
+                        htmlf("</td><td colspan='%d' /></tr>\n", cols);
+                        strbuf_setlen(&graphbuf, 0);
+                }
+                /* Current commit's graph segment is now ready in graphbuf */
+        }
 
         info = cgit_parse_commit(commit);
         htmlf("<tr%s><td>",
                 ctx.qry.showmsg ? " class='logheader'" : "");
         tmp = fmt("id=%s", sha1_to_hex(commit->object.sha1));
         tmp = cgit_fileurl(ctx.repo->url, "commit", ctx.qry.vpath, tmp);
         html_link_open(tmp, NULL, NULL);
         cgit_print_age(commit->date, TM_WEEK * 2, FMT_SHORTDATE);
         html_link_close();
-        htmlf("</td><td%s>",
-                ctx.qry.showmsg ? " class='logsubject'" : "");
+        html("</td>");
+
+        if (revs->graph) {
+                /* Print graph segment for current commit */
+                html("<td class='commitgraph'>");
+                html(graphbuf.buf);
+                html("</td>");
+                strbuf_setlen(&graphbuf, 0);
+        }
+
+        htmlf("<td%s>", ctx.qry.showmsg ? " class='logsubject'" : "");
         cgit_commit_link(info->subject, NULL, NULL, ctx.qry.head,
                          sha1_to_hex(commit->object.sha1), ctx.qry.vpath, 0);
         show_commit_decorations(commit);
         html("</td><td>");
         html_txt(info->author);
         if (ctx.repo->enable_log_filecount) {
                 files = 0;
                 add_lines = 0;
@@ -107,42 +135,69 @@ void print_commit(struct commit *commit)
                 htmlf("%d", files);
                 if (ctx.repo->enable_log_linecount) {
                         html("</td><td>");
                         htmlf("-%d/+%d", rem_lines, add_lines);
                 }
         }
         html("</td></tr>\n");
 
-        if (ctx.qry.showmsg) { /* Print message + notes in a second table row */
-                /* Concatenate commit message and notes in msgbuf */
+        if (revs->graph || ctx.qry.showmsg) { /* Print a second table row */
                 struct strbuf msgbuf = STRBUF_INIT;
-                if (info->msg && *(info->msg)) {
-                        strbuf_addstr(&msgbuf, info->msg);
+                html("<tr class='nohover'><td/>"); /* Empty 'Age' column */
+
+                if (ctx.qry.showmsg) {
+                        /* Concatenate commit message + notes in msgbuf */
+                        if (info->msg && *(info->msg)) {
+                                strbuf_addstr(&msgbuf, info->msg);
+                                strbuf_addch(&msgbuf, '\n');
+                        }
+                        format_note(NULL, commit->object.sha1, &msgbuf,
+                                    PAGE_ENCODING,
+                                    NOTES_SHOW_HEADER | NOTES_INDENT);
                         strbuf_addch(&msgbuf, '\n');
+                        strbuf_ltrim(&msgbuf);
                 }
-                format_note(NULL, commit->object.sha1, &msgbuf, PAGE_ENCODING,
-                            NOTES_SHOW_HEADER | NOTES_INDENT);
-                strbuf_addch(&msgbuf, '\n');
-                strbuf_ltrim(&msgbuf);
 
-                if (ctx.repo->enable_log_filecount) {
-                        cols++;
-                        if (ctx.repo->enable_log_linecount)
-                                cols++;
+                if (revs->graph) {
+                        int lines = 0;
+
+                        /* Calculate graph padding */
+                        if (ctx.qry.showmsg) {
+                                /* Count #lines in commit message + notes */
+                                const char *p = msgbuf.buf;
+                                lines = 1;
+                                while ((p = strchr(p, '\n'))) {
+                                        p++;
+                                        lines++;
+                                }
+                        }
+
+                        /* Print graph padding */
+                        html("<td class='commitgraph'>");
+                        while (lines > 0 || !graph_is_commit_finished(revs->graph)) {
+                                if (graphbuf.len)
+                                        html("\n");
+                                strbuf_setlen(&graphbuf, 0);
+                                graph_next_line(revs->graph, &graphbuf);
+                                html(graphbuf.buf);
+                                lines--;
+                        }
+                        html("</td>\n");
                 }
 
-                /* Create second table row containing msgbuf */
-                htmlf("<tr class='nohover'><td/><td colspan='%d' class='logmsg'>",
-                        cols);
+                /* Print msgbuf into remainder of table row */
+                htmlf("<td colspan='%d'%s>\n", cols,
+                        ctx.qry.showmsg ? " class='logmsg'" : "");
                 html_txt(msgbuf.buf);
                 html("</td></tr>\n");
                 strbuf_release(&msgbuf);
         }
 
+        strbuf_release(&graphbuf);
         cgit_free_commitinfo(info);
 }
 
 static const char *disambiguate_ref(const char *ref)
 {
         unsigned char sha1[20];
         const char *longref;
 
@@ -211,16 +266,20 @@ void cgit_print_log(const char *tip, int ofs, int cnt, char *grep, char *pattern
                                         fprintf(stderr, "Bad range expr: %s\n",
                                                 arg);
                                         break;
                                 }
                                 vector_push(&vec, &arg, 0);
                         }
                 }
         }
+        if (ctx.repo->enable_commit_graph) {
+                static const char *graph_arg = "--graph";
+                vector_push(&vec, &graph_arg, 0);
+        }
 
         if (path) {
                 arg = "--";
                 vector_push(&vec, &arg, 0);
                 vector_push(&vec, &path, 0);
         }
 
         /* Make sure the vector is NULL-terminated */
@@ -237,18 +296,20 @@ void cgit_print_log(const char *tip, int ofs, int cnt, char *grep, char *pattern
         rev.show_decorations = 1;
         rev.grep_filter.regflags |= REG_ICASE;
         compile_grep_patterns(&rev.grep_filter);
         prepare_revision_walk(&rev);
 
         if (pager)
                 html("<table class='list nowrap'>");
 
-        html("<tr class='nohover'><th class='left'>Age</th>"
-              "<th class='left'>Commit message");
+        html("<tr class='nohover'><th class='left'>Age</th>");
+        if (ctx.repo->enable_commit_graph)
+                html("<th></th>");
+        html("<th class='left'>Commit message");
         if (pager) {
                 html(" (");
                 cgit_log_link(ctx.qry.showmsg ? "Collapse" : "Expand", NULL,
                               NULL, ctx.qry.head, ctx.qry.sha1,
                               ctx.qry.vpath, ctx.qry.ofs, ctx.qry.grep,
                               ctx.qry.search, ctx.qry.showmsg ? 0 : 1);
                 html(")");
         }
@@ -269,17 +330,17 @@ void cgit_print_log(const char *tip, int ofs, int cnt, char *grep, char *pattern
         for (i = 0; i < ofs && (commit = get_revision(&rev)) != NULL; i++) {
                 free(commit->buffer);
                 commit->buffer = NULL;
                 free_commit_list(commit->parents);
                 commit->parents = NULL;
         }
 
         for (i = 0; i < cnt && (commit = get_revision(&rev)) != NULL; i++) {
-                print_commit(commit);
+                print_commit(commit, &rev);
                 free(commit->buffer);
                 commit->buffer = NULL;
                 free_commit_list(commit->parents);
                 commit->parents = NULL;
         }
         if (pager) {
                 html("</table><div class='pager'>");
                 if (ofs > 0) {