Add support for including a footer on all pages

The new cgitrc option `footer` can be used to include a html-file which
replaces the standard 'generated by cgit' message at the bottom of each
page.

Suggested-by: Peter Danenberg <pcd@wikitex.org>
Signed-off-by: Lars Hjemli <hjemli@gmail.com>

cgit.c

@@ -25,6 +25,8 @@ void config_cb(const char *name, const char *value)
 		ctx.cfg.root_readme = xstrdup(value);
 	else if (!strcmp(name, "css"))
 		ctx.cfg.css = xstrdup(value);
+	else if (!strcmp(name, "footer"))
+		ctx.cfg.footer = xstrdup(value);
 	else if (!strcmp(name, "logo"))
 		ctx.cfg.logo = xstrdup(value);
 	else if (!strcmp(name, "index-header"))

cgit.h

@@ -125,6 +125,7 @@ struct cgit_config {
 	char *cache_root;
 	char *clone_prefix;
 	char *css;
+	char *footer;
 	char *index_header;
 	char *index_info;
 	char *logo;

ui-shared.c

@@ -443,10 +443,16 @@ void cgit_print_docstart(struct cgit_context *ctx)
 
 void cgit_print_docend()
 {
-	html("</div><div class='footer'>generated ");
+	html("</div>");
+	if (ctx.cfg.footer)
+		html_include(ctx.cfg.footer);
+	else {
+		html("<div class='footer'>generated ");
 		cgit_print_date(time(NULL), FMT_LONGDATE);
 		htmlf(" by cgit %s", cgit_version);
-	html("</div>\n</body>\n</html>\n");
+		html("</div>\n");
+	}
+	html("</body>\n</html>\n");
 }
 
 int print_branch_option(const char *refname, const unsigned char *sha1,