Expose buffer list to shell over $kak_buflist

README.asciidoc

@@ -911,6 +911,7 @@ Some of Kakoune state is available through environment variables:
  * +kak_selections+: content of the selection separated by colons, colons in
     the selection contents are escapted with a backslash.
  * +kak_bufname+: name of the current buffer
+ * +kak_buflist+: the current buffer list, each buffer seperated by a colon
  * +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

src/main.cc

@@ -56,6 +56,17 @@ void register_env_vars()
             "buffile",
             [](StringView name, const Context& context) -> String
             { return context.buffer().name(); }
+        }, {
+            "buflist",
+            [](StringView name, const Context& context)
+            {
+                String res;
+                for (auto& buf : BufferManager::instance())
+                {
+                    res += buf->display_name() + ":";
+                }
+                res.pop_back();
+                return res; }
         }, {
             "timestamp",
             [](StringView name, const Context& context)