commands starting with horizontal whitespace don't go into the history

README.asciidoc

@@ -466,7 +466,9 @@ Commands
 When pressing `:` in normal mode, Kakoune will open a prompt to enter a command.
 
 Commands are used for non editing tasks, such as opening a buffer, writing the
-current one, quitting, etc.
+current one, quitting, etc. You can cycle through the command history with
+`<c-p>` and `<c-n>`. Commands starting with horizontal whitespace (e.g. a
+space) will not be saved in the command history.
 
 Basic Commands
 ~~~~~~~~~~~~~~

src/input_handler.cc

@@ -842,7 +842,7 @@ private:
 
     static void history_push(History& history, StringView entry)
     {
-        if(entry.empty())
+        if(entry.empty() or is_horizontal_blank(entry[0_byte]))
         {
             return;
         }