options: properly reset directories on 'autochdir' (#9894)

Fixes https://github.com/neovim/neovim/issues/9892

src/nvim/api/vim.c

@@ -594,7 +594,7 @@ void nvim_set_current_dir(String dir, Error *err)
     return;
   }
 
-  post_chdir(kCdScopeGlobal);
+  post_chdir(kCdScopeGlobal, true);
   try_end(err);
 }
 

src/nvim/buffer.c

@@ -1559,6 +1559,7 @@ void do_autochdir(void)
     if (starting == 0
         && curbuf->b_ffname != NULL
         && vim_chdirfile(curbuf->b_ffname) == OK) {
+      post_chdir(kCdScopeGlobal, false);
       shorten_fnames(true);
     }
   }

src/nvim/ex_docmd.c

@@ -7218,7 +7218,7 @@ void free_cd_dir(void)
 /// Deal with the side effects of changing the current directory.
 ///
 /// @param scope  Scope of the function call (global, tab or window).
-void post_chdir(CdScope scope)
+void post_chdir(CdScope scope, bool trigger_dirchanged)
 {
   // Always overwrite the window-local CWD.
   xfree(curwin->w_localdir);
@@ -7258,7 +7258,10 @@ void post_chdir(CdScope scope)
   }
 
   shorten_fnames(true);
-  do_autocmd_dirchanged(cwd, scope);
+
+  if (trigger_dirchanged) {
+    do_autocmd_dirchanged(cwd, scope);
+  }
 }
 
 /// `:cd`, `:tcd`, `:lcd`, `:chdir`, `:tchdir` and `:lchdir`.
@@ -7320,7 +7323,7 @@ void ex_cd(exarg_T *eap)
     if (vim_chdir(new_dir, scope)) {
       EMSG(_(e_failed));
     } else {
-      post_chdir(scope);
+      post_chdir(scope, true);
       // Echo the new current directory if the command was typed.
       if (KeyTyped || p_verbose >= 5) {
         ex_pwd(eap);

test/functional/ex_cmds/cd_spec.lua

@@ -286,6 +286,15 @@ describe("getcwd()", function ()
     command("call delete('../"..directories.global.."', 'd')")
     eq("", helpers.eval("getcwd()"))
   end)
+
+  it("works with 'autochdir' after local directory was set (#9892)", function()
+    local curdir = cwd()
+    command('lcd ' .. directories.global)
+    command('lcd -')
+    command('set autochdir')
+    command('edit ' .. directories.global .. '/foo')
+    eq(curdir .. pathsep .. directories.global, cwd())
+  end)
 end)