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);