Expose kak_buf_line_count

README.asciidoc

@@ -780,6 +780,7 @@ Some of Kakoune state is available through environment variables:
  * `kak_buffile`: full path of the file or same as `kak_bufname` when
        there's no associated file
  * `kak_buflist`: the current buffer list, each buffer separated by a colon
+ * `kak_buf_line_count`: the current buffer line count
  * `kak_timestamp`: timestamp of the current buffer, the timestamp is an
        integer value which is incremented each time the buffer is modified.
  * `kak_runtime`: directory containing the kak binary

doc/manpages/expansions.asciidoc

@@ -69,6 +69,8 @@ informations about Kakoune's state:
 	associated file
 *kak_buflist*::
 	the current buffer list, each buffer separated by a colon
+*kak_buf_line_count*::
+	the current buffer line count
 *kak_timestamp*::
 	timestamp of the current buffer, the timestamp is an integer value
 	which is incremented each time the buffer is modified

src/main.cc

@@ -93,6 +93,10 @@ void register_env_vars()
             [](StringView name, const Context& context)
             { return join(BufferManager::instance() |
                           transform(std::mem_fn(&Buffer::display_name)), ':'); }
+        }, {
+            "buf_line_count", false,
+            [](StringView name, const Context& context) -> String
+            { return to_string(context.buffer().line_count()); }
         }, {
             "timestamp", false,
             [](StringView name, const Context& context) -> String