vim-patch:8.2.3920: restoring directory after using another window is inefficient

Problem:    Restoring directory after using another window is inefficient.
Solution:   Only restore the directory for win_execute().  Apply 'autochdir'
            only when needed.
90c317f224

src/nvim/testdir/test_autochdir.vim

@@ -53,6 +53,27 @@ func Test_set_filename_other_window()
   endtry
 endfunc
 
+func Test_acd_win_execute()
+  CheckFunction test_autochdir
+  let cwd = getcwd()
+  set acd
+  call test_autochdir()
+
+  call mkdir('Xfile')
+  let winid = win_getid()
+  new Xfile/file
+  call assert_match('testdir.Xfile$', getcwd())
+  cd ..
+  call assert_match('testdir$', getcwd())
+  call win_execute(winid, 'echo')
+  call assert_match('testdir$', getcwd())
+
+  bwipe!
+  set noacd
+  call chdir(cwd)
+  call delete('Xfile', 'rf')
+endfunc
+
 func Test_verbose_pwd()
   CheckFunction test_autochdir
   let cwd = getcwd()

src/nvim/window.c

@@ -6767,9 +6767,6 @@ void restore_win_noblock(switchwin_T *switchwin, bool no_display)
     curwin = switchwin->sw_curwin;
     curbuf = curwin->w_buffer;
   }
-  // If called by win_execute() and executing the command changed the
-  // directory, it now has to be restored.
-  fix_current_dir();
 }
 
 /// Make "buf" the current buffer.

src/nvim/window.h

@@ -5,6 +5,7 @@
 
 #include "nvim/buffer_defs.h"
 #include "nvim/mark.h"
+#include "nvim/os/os.h"
 
 // Values for file_name_in_line()
 #define FNAME_MESS      1       // give error message
@@ -47,12 +48,27 @@ typedef struct {
   do { \
     win_T *const wp_ = (wp); \
     const pos_T curpos_ = wp_->w_cursor; \
+    char_u cwd_[MAXPATHL]; \
+    char_u autocwd_[MAXPATHL]; \
+    bool apply_acd_ = false; \
+    const int cwd_status_ = os_dirname(cwd_, MAXPATHL); \
+    /* If 'acd' is set, check we are using that directory.  If yes, then */ \
+    /* apply 'acd' afterwards, otherwise restore the current directory. */ \
+    if (cwd_status_ == OK && p_acd) { \
+      do_autochdir(); \
+      apply_acd_ = os_dirname(autocwd_, MAXPATHL) == OK && STRCMP(cwd_, autocwd_) == 0; \
+    } \
     switchwin_T switchwin_; \
     if (switch_win_noblock(&switchwin_, wp_, (tp), true) == OK) { \
       check_cursor(); \
       block; \
     } \
     restore_win_noblock(&switchwin_, true); \
+    if (apply_acd_) { \
+      do_autochdir(); \
+    } else if (cwd_status_ == OK) { \
+      os_chdir((char *)cwd_); \
+    } \
     /* Update the status line if the cursor moved. */ \
     if (win_valid(wp_) && !equalpos(curpos_, wp_->w_cursor)) { \
       wp_->w_redr_status = true; \

test/functional/legacy/autochdir_spec.lua

@@ -61,6 +61,20 @@ describe('autochdir behavior', function()
     expected_empty()
   end)
 
+  it('win_execute() does not change directory', function()
+    local subdir = 'Xfile'
+    command('cd '..dir)
+    command('set autochdir')
+    call('mkdir', subdir)
+    local winid = eval('win_getid()')
+    command('new '..subdir..'/file')
+    matches('.*'..dir..'[/\\]'..subdir, eval('getcwd()'))
+    command('cd ..')
+    matches('.*'..dir, eval('getcwd()'))
+    call('win_execute', winid, 'echo')
+    matches('.*'..dir, eval('getcwd()'))
+  end)
+
   it(':verbose pwd shows whether autochdir is used', function()
     local subdir = 'Xautodir'
     command('cd '..dir)