src/Pure/General/mercurial.scala

       command("id " + options + opt_rev(rev)).check.out_lines.headOption getOrElse ""
 
     def manifest(rev: String = "", options: String = ""): List[String] =
       command("manifest " + options + opt_rev(rev)).check.out_lines
 
-    def log(rev: String = "", options: String = ""): String =
-      Library.trim_line(command("log " + options + opt_rev(rev)).check.out)
+    def log(rev: String = "", template: String = "", options: String = ""): String =
+      Library.trim_line(command("log " + options + opt_rev(rev) + opt_template(template)).check.out)
 
     def pull(remote: String = "", rev: String = "", options: String = ""): Unit =
       command("pull " + options + opt_rev(rev) + optional(remote)).check
 
     def update(rev: String = "", clean: Boolean = false, check: Boolean = false, options: String = "")