Capture and re-export $NVIM_APPNAME when it's defined

README.md

@@ -95,6 +95,8 @@ Temporarily disabling (and re-enabling) Firenvim in a tab can be done either by
 
 ### Building a Firenvim-specific config
 
+**New**: With Neovim nightly builds from 2023/02/17 or more recent, you can use [$NVIM_APPNAME](https://neovim.io/doc/user/starting.html#$NVIM_APPNAME) to define a completely separate firenvim config. In order to do that, make sure "NVIM_APPNAME" is appropriately set when you run firenvim#install().
+
 When it starts Neovim, Firenvim sets the variable `g:started_by_firenvim` which you can check to run different code in your init.vim. For example:
 
 ```vim

autoload/firenvim.vim

@@ -636,6 +636,7 @@ function! s:get_executable_content(data_dir, prolog) abort
                                 \ s:capture_env_var('XDG_CONFIG_DIRS') .
                                 \ s:capture_env_var('XDG_CACHE_HOME') .
                                 \ s:capture_env_var('XDG_RUNTIME_DIR') .
+                                \ s:capture_env_var('NVIM_APPNAME') .
                                 \ a:prolog . "\n" .
                                 \ "exec '" . s:get_progpath() .
                                   \ "' --headless " . l:stdioopen .