feat(exrc): search in parent directories (#33889)

feat(exrc): search exrc in parent directories

Problem:
`.nvim.lua` is only loaded from current directory, which is not flexible
when working from a subfolder of the project.

Solution:
Also search parent directories for configuration file.

runtime/doc/news.txt

@@ -122,6 +122,7 @@ DEFAULTS
 
 • 'statusline' default is exposed as a statusline expression (previously it
   was implemented as an internal C routine).
+• Project-local configuration ('exrc') is also loaded from parent directories.
 
 DIAGNOSTICS
 

runtime/doc/options.txt

@@ -2412,9 +2412,9 @@ A jump table for the options with a short description can be found at |Q_op|.
 'exrc' 'ex'		boolean	(default off)
 			global
 	Enables project-local configuration. Nvim will execute any .nvim.lua,
-	.nvimrc, or .exrc file found in the |current-directory|, if the file is
-	in the |trust| list. Use |:trust| to manage trusted files. See also
-	|vim.secure.read()|.
+	.nvimrc, or .exrc file found in the |current-directory| and all parent
+	directories (ordered upwards), if the files are in the |trust| list.
+	Use |:trust| to manage trusted files. See also |vim.secure.read()|.
 
 	Compare 'exrc' to |editorconfig|:
 	- 'exrc' can execute any code; editorconfig only specifies settings.

runtime/doc/vim_diff.txt

@@ -209,6 +209,10 @@ nvim.swapfile:
   swapfile is owned by a running Nvim process. Shows |W325| "Ignoring
   swapfile…" message.
 
+nvim.find_exrc:
+- VimEnter: Extend 'exrc' to also search for project-local configuration files
+  in all parent directories.
+
 ==============================================================================
 New Features                                                   *nvim-features*