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>

6 files changed, 112 insertions, 23 deletions

diff --git a/cgit.c b/cgit.c
index 412fbf0..53ab68d 100644
--- a/cgit.c
+++ b/cgit.c
@@ -57,6 +57,8 @@ void repo_config(struct cgit_repo *repo, const char *name, const char *value)
                 repo->defbranch = xstrdup(value);
         else if (!strcmp(name, "snapshots"))
                 repo->snapshots = ctx.cfg.snapshots & cgit_parse_snapshots_mask(value);
+        else if (!strcmp(name, "enable-commit-graph"))
+                repo->enable_commit_graph = ctx.cfg.enable_commit_graph * atoi(value);
         else if (!strcmp(name, "enable-log-filecount"))
                 repo->enable_log_filecount = ctx.cfg.enable_log_filecount * atoi(value);
         else if (!strcmp(name, "enable-log-linecount"))
@@ -141,6 +143,8 @@ void config_cb(const char *name, const char *value)
                 ctx.cfg.enable_gitweb_owner = atoi(value);
         else if (!strcmp(name, "enable-index-links"))
                 ctx.cfg.enable_index_links = atoi(value);
+        else if (!strcmp(name, "enable-commit-graph"))
+                ctx.cfg.enable_commit_graph = atoi(value);
         else if (!strcmp(name, "enable-log-filecount"))
                 ctx.cfg.enable_log_filecount = atoi(value);
         else if (!strcmp(name, "enable-log-linecount"))
@@ -540,6 +544,8 @@ void print_repo(FILE *f, struct cgit_repo *repo)
                 fprintf(f, "repo.section=%s\n", repo->section);
         if (repo->clone_url)
                 fprintf(f, "repo.clone-url=%s\n", repo->clone_url);
+        fprintf(f, "repo.enable-commit-graph=%d\n",
+                repo->enable_commit_graph);
         fprintf(f, "repo.enable-log-filecount=%d\n",
                 repo->enable_log_filecount);
         fprintf(f, "repo.enable-log-linecount=%d\n",
diff --git a/cgit.css b/cgit.css
index 7a5f423..7600e84 100644
--- a/cgit.css
+++ b/cgit.css
@@ -153,6 +153,11 @@ table.list td {
         padding: 0.1em 0.5em 0.1em 0.5em;
 }
 
+table.list td.commitgraph {
+        font-family: monospace;
+        white-space: pre;
+}
+
 table.list td.logsubject {
         font-family: monospace;
         font-weight: bold;
@@ -731,4 +736,4 @@ table.ssdiff td.space {
 
 table.ssdiff td.space div {
         min-height: 3em;
-}
\ No newline at end of file
+}
diff --git a/cgit.h b/cgit.h
index f5f68ac..bed770b 100644
--- a/cgit.h
+++ b/cgit.h
@@ -20,6 +20,7 @@
 #include <xdiff/xdiff.h>
 #include <utf8.h>
 #include <notes.h>
+#include <graph.h>
 
 
 /*
@@ -71,6 +72,7 @@ struct cgit_repo {
         char *section;
         char *clone_url;
         int snapshots;
+        int enable_commit_graph;
         int enable_log_filecount;
         int enable_log_linecount;
         int enable_remote_branches;
@@ -188,6 +190,7 @@ struct cgit_config {
         int enable_filter_overrides;
         int enable_gitweb_owner;
         int enable_index_links;
+        int enable_commit_graph;
         int enable_log_filecount;
         int enable_log_linecount;
         int enable_remote_branches;
diff --git a/cgitrc.5.txt b/cgitrc.5.txt
index 75b6584..b45c46b 100644
--- a/cgitrc.5.txt
+++ b/cgitrc.5.txt
@@ -90,7 +90,12 @@ embedded::
         Flag which, when set to "1", will make cgit generate a html fragment
         suitable for embedding in other html pages. Default value: none. See
         also: "noheader".
-        
+
+enable-commit-graph::
+        Flag which, when set to "1", will make cgit print an ASCII-art commit
+        history graph to the left of the commit messages in the repository
+        log page. Default value: "0".
+
 enable-filter-overrides::
         Flag which, when set to "1", allows all filter settings to be
         overridden in repository-specific cgitrc files. Default value: none.
@@ -354,6 +359,10 @@ repo.defbranch::
 repo.desc::
         The value to show as repository description. Default value: none.
 
+repo.enable-commit-graph::
+        A flag which can be used to disable the global setting
+        `enable-commit-graph'. Default value: none.
+
 repo.enable-log-filecount::
         A flag which can be used to disable the global setting
         `enable-log-filecount'. Default value: none.
@@ -441,6 +450,10 @@ css=/css/cgit.css
 enable-index-links=1
 
 
+# Enable ASCII art commit history graph on the log pages
+enable-commit-graph=1
+
+
 # Show number of affected files per commit on the log pages
 enable-log-filecount=1
 
diff --git a/shared.c b/shared.c
index 765cd27..7ec2e19 100644
--- a/shared.c
+++ b/shared.c
@@ -56,6 +56,7 @@ struct cgit_repo *cgit_add_repo(const char *url)
         ret->section = ctx.cfg.section;
         ret->defbranch = "master";
         ret->snapshots = ctx.cfg.snapshots;
+        ret->enable_commit_graph = ctx.cfg.enable_commit_graph;
         ret->enable_log_filecount = ctx.cfg.enable_log_filecount;
         ret->enable_log_linecount = ctx.cfg.enable_log_linecount;
         ret->enable_remote_branches = ctx.cfg.enable_remote_branches;
diff --git a/ui-log.c b/ui-log.c
index 6d7fcae..0d86fd5 100644
--- a/ui-log.c
+++ b/ui-log.c
@@ -77,11 +77,30 @@ void show_commit_decorations(struct commit *commit)
         }
 }
 
-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>",
@@ -91,8 +110,17 @@ void print_commit(struct commit *commit)
         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);
@@ -112,32 +140,59 @@ void print_commit(struct commit *commit)
         }
         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);
 }
 
@@ -216,6 +271,10 @@ void cgit_print_log(const char *tip, int ofs, int cnt, char *grep, char *pattern
                         }
                 }
         }
+        if (ctx.repo->enable_commit_graph) {
+                static const char *graph_arg = "--graph";
+                vector_push(&vec, &graph_arg, 0);
+        }
 
         if (path) {
                 arg = "--";
@@ -242,8 +301,10 @@ void cgit_print_log(const char *tip, int ofs, int cnt, char *grep, char *pattern
         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,
@@ -274,7 +335,7 @@ void cgit_print_log(const char *tip, int ofs, int cnt, char *grep, char *pattern
         }
 
         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);