vim-patch:8.0.1459: cannot handle change of directory

Problem:    Cannot handle change of directory.
Solution:   Add the DirChanged autocommand event. (Andy Massimino,
            closes vim/vim#888)  Avoid changing directory for 'autochdir' too often.
https://github.com/vim/vim/commit/b7407d3fc9496f9048fb65ab17b5ba3444965c0e

Only add "auto" pattern. "window" and "global" are already implemented.
Skip `Test_dirchanged_auto` using `CheckFunction test_autochdir`.
Part of PR #15952. More information can be found there.

N/A patches for version.c:

vim-patch:8.0.1460: missing file in patch

Problem:    Missing file in patch.
Solution:   Add changes to missing file.
https://github.com/vim/vim/commit/b5cb65ba2bcc6bbc6d2798a2dea18b95f0b38f5e

vim-patch:8.0.1461: missing another file in patch

Problem:    Missing another file in patch.
Solution:   Add changes to missing file.
https://github.com/vim/vim/commit/15833239a4131279935a4bd574b74fe3a2b0f49f

9 files changed, 94 insertions, 14 deletions

diff --git a/runtime/doc/autocmd.txt b/runtime/doc/autocmd.txt
index 5923dada43..b7df0fba54 100644
--- a/runtime/doc/autocmd.txt
+++ b/runtime/doc/autocmd.txt
@@ -519,11 +519,17 @@ DiffUpdated			After diffs have been updated.  Depending on
 				change or when doing |:diffupdate|.
 							*DirChanged*
 DirChanged			After the |current-directory| was changed.
+				The pattern can be:
+					"window" to trigger on `:lcd`
+					"tab"    to trigger on `:tcd`
+					"global" to trigger on `:cd`
+					"auto"   to trigger on 'autochdir'.
 				Sets these |v:event| keys:
 				    cwd:   current working directory
 				    scope: "global", "tab", "window"
 				    changed_window: v:true if we fired the event
 				                    switching window (or tab)
+				<afile> is set to the new directory name.
 				Non-recursive (event cannot trigger itself).
 							*FileAppendCmd*
 FileAppendCmd			Before appending to a file.  Should do the
diff --git a/runtime/doc/vim_diff.txt b/runtime/doc/vim_diff.txt
index 64824b2e3f..c85cae4004 100644
--- a/runtime/doc/vim_diff.txt
+++ b/runtime/doc/vim_diff.txt
@@ -180,6 +180,7 @@ Commands:
   |:match| can be invoked before highlight group is defined
 
 Events:
+  |DirChanged| can be triggered when switching to another window
   |Signal|
   |TabNewEntered|
   |TermClose|
diff --git a/src/nvim/buffer.c b/src/nvim/buffer.c
index 37cc854959..386714b05a 100644
--- a/src/nvim/buffer.c
+++ b/src/nvim/buffer.c
@@ -593,9 +593,6 @@ bool close_buffer(win_T *win, buf_T *buf, int action, bool abort_if_last)
     buf->b_nwindows--;
   }
 
-  // Change directories when the 'acd' option is set.
-  do_autochdir();
-
   // Disable buffer-updates for the current buffer.
   // No need to check `unload_buf`: in that case the function returned above.
   buf_updates_unload(buf, false);
@@ -1628,7 +1625,7 @@ void do_autochdir(void)
   if (p_acd) {
     if (starting == 0
         && curbuf->b_ffname != NULL
-        && vim_chdirfile(curbuf->b_ffname) == OK) {
+        && vim_chdirfile(curbuf->b_ffname, kCdCauseAuto) == OK) {
       post_chdir(kCdScopeGlobal, false);
       shorten_fnames(true);
     }
diff --git a/src/nvim/ex_docmd.c b/src/nvim/ex_docmd.c
index 16a9b78c6a..5d83e2218b 100644
--- a/src/nvim/ex_docmd.c
+++ b/src/nvim/ex_docmd.c
@@ -7749,7 +7749,7 @@ void post_chdir(CdScope scope, bool trigger_dirchanged)
   shorten_fnames(true);
 
   if (trigger_dirchanged) {
-    do_autocmd_dirchanged(cwd, scope, false);
+    do_autocmd_dirchanged(cwd, scope, kCdCauseManual);
   }
 }
 
diff --git a/src/nvim/ex_session.c b/src/nvim/ex_session.c
index 1e1da6a9a3..0dfd7e1edd 100644
--- a/src/nvim/ex_session.c
+++ b/src/nvim/ex_session.c
@@ -963,7 +963,7 @@ void ex_mkrc(exarg_T *eap)
           *dirnow = NUL;
         }
         if (*dirnow != NUL && (ssop_flags & SSOP_SESDIR)) {
-          if (vim_chdirfile((char_u *)fname) == OK) {
+          if (vim_chdirfile((char_u *)fname, kCdCauseOther) == OK) {
             shorten_fnames(true);
           }
         } else if (*dirnow != NUL
diff --git a/src/nvim/file_search.c b/src/nvim/file_search.c
index 5458d8acf2..e7c4785beb 100644
--- a/src/nvim/file_search.c
+++ b/src/nvim/file_search.c
@@ -1590,7 +1590,7 @@ theend:
   return file_name;
 }
 
-void do_autocmd_dirchanged(char *new_dir, CdScope scope, bool changed_window)
+void do_autocmd_dirchanged(char *new_dir, CdScope scope, CdCause cause)
 {
   static bool recursive = false;
 
@@ -1621,10 +1621,22 @@ void do_autocmd_dirchanged(char *new_dir, CdScope scope, bool changed_window)
   }
 
   tv_dict_add_str(dict, S_LEN("scope"), buf);  // -V614
-  tv_dict_add_str(dict, S_LEN("cwd"),   new_dir);
-  tv_dict_add_bool(dict, S_LEN("changed_window"), changed_window);
+  tv_dict_add_str(dict, S_LEN("cwd"), new_dir);
+  tv_dict_add_bool(dict, S_LEN("changed_window"), cause == kCdCauseWindow);
   tv_dict_set_keys_readonly(dict);
 
+  switch (cause) {
+  case kCdCauseManual:
+  case kCdCauseWindow:
+    break;
+  case kCdCauseAuto:
+    snprintf(buf, sizeof(buf), "auto");
+    break;
+  case kCdCauseOther:
+    // Should never happen.
+    abort();
+  }
+
   apply_autocmds(EVENT_DIRCHANGED, (char_u *)buf, (char_u *)new_dir, false,
                  curbuf);
 
@@ -1636,7 +1648,7 @@ void do_autocmd_dirchanged(char *new_dir, CdScope scope, bool changed_window)
 /// Change to a file's directory.
 /// Caller must call shorten_fnames()!
 /// @return OK or FAIL
-int vim_chdirfile(char_u *fname)
+int vim_chdirfile(char_u *fname, CdCause cause)
 {
   char dir[MAXPATHL];
 
@@ -1654,8 +1666,8 @@ int vim_chdirfile(char_u *fname)
 #ifdef BACKSLASH_IN_FILENAME
   slash_adjust((char_u *)dir);
 #endif
-  if (!strequal(dir, (char *)NameBuff)) {
-    do_autocmd_dirchanged(dir, kCdScopeWindow, false);
+  if (cause != kCdCauseOther && !strequal(dir, (char *)NameBuff)) {
+    do_autocmd_dirchanged(dir, kCdScopeWindow, cause);
   }
 
   return OK;
diff --git a/src/nvim/globals.h b/src/nvim/globals.h
index 8a36b3bedd..e04856e85f 100644
--- a/src/nvim/globals.h
+++ b/src/nvim/globals.h
@@ -1042,6 +1042,14 @@ typedef enum {
 #define MIN_CD_SCOPE  kCdScopeWindow
 #define MAX_CD_SCOPE  kCdScopeGlobal
 
+/// What caused the current directory to change.
+typedef enum {
+  kCdCauseOther = -1,
+  kCdCauseManual,  ///< Using `:cd`, `:tcd`, `:lcd` or `chdir()`.
+  kCdCauseWindow,  ///< Switching to another window.
+  kCdCauseAuto,    ///< On 'autochdir'.
+} CdCause;
+
 // Only filled for Win32.
 EXTERN char windowsVersion[20] INIT(= { 0 });
 
diff --git a/src/nvim/testdir/test_autocmd.vim b/src/nvim/testdir/test_autocmd.vim
index 015979e1be..d174b11a9c 100644
--- a/src/nvim/testdir/test_autocmd.vim
+++ b/src/nvim/testdir/test_autocmd.vim
@@ -1328,6 +1328,62 @@ func Test_autocommand_all_events()
   call assert_fails('au * x bwipe', 'E1155:')
 endfunc
 
+function s:Before_test_dirchanged()
+  augroup test_dirchanged
+    autocmd!
+  augroup END
+  let s:li = []
+  let s:dir_this = getcwd()
+  let s:dir_other = s:dir_this . '/foo'
+  call mkdir(s:dir_other)
+endfunc
+
+function s:After_test_dirchanged()
+  exe 'cd' s:dir_this
+  call delete(s:dir_other, 'd')
+  augroup test_dirchanged
+    autocmd!
+  augroup END
+endfunc
+
+function Test_dirchanged_global()
+  call s:Before_test_dirchanged()
+  autocmd test_dirchanged DirChanged global call add(s:li, "cd:")
+  autocmd test_dirchanged DirChanged global call add(s:li, expand("<afile>"))
+  exe 'cd' s:dir_other
+  call assert_equal(["cd:", s:dir_other], s:li)
+  exe 'lcd' s:dir_other
+  call assert_equal(["cd:", s:dir_other], s:li)
+  call s:After_test_dirchanged()
+endfunc
+
+function Test_dirchanged_local()
+  call s:Before_test_dirchanged()
+  autocmd test_dirchanged DirChanged window call add(s:li, "lcd:")
+  autocmd test_dirchanged DirChanged window call add(s:li, expand("<afile>"))
+  exe 'cd' s:dir_other
+  call assert_equal([], s:li)
+  exe 'lcd' s:dir_other
+  call assert_equal(["lcd:", s:dir_other], s:li)
+  call s:After_test_dirchanged()
+endfunc
+
+function Test_dirchanged_auto()
+  call s:Before_test_dirchanged()
+  call test_autochdir()
+  autocmd test_dirchanged DirChanged auto call add(s:li, "auto:")
+  autocmd test_dirchanged DirChanged auto call add(s:li, expand("<afile>"))
+  set acd
+  exe 'cd ..'
+  call assert_equal([], s:li)
+  exe 'edit ' . s:dir_other . '/Xfile'
+  call assert_equal(s:dir_other, getcwd())
+  call assert_equal(["auto:", s:dir_other], s:li)
+  set noacd
+  bwipe!
+  call s:After_test_dirchanged()
+endfunc
+
 " Test TextChangedI and TextChangedP
 " See test/functional/viml/completion_spec.lua'
 func Test_ChangedP()
diff --git a/src/nvim/window.c b/src/nvim/window.c
index 1fe4aa1add..a7470889b3 100644
--- a/src/nvim/window.c
+++ b/src/nvim/window.c
@@ -4542,7 +4542,7 @@ static void win_enter_ext(win_T *const wp, const int flags)
     if (os_chdir(new_dir) == 0) {
       if (!p_acd && !strequal(new_dir, cwd)) {
         do_autocmd_dirchanged(new_dir, curwin->w_localdir
-                              ? kCdScopeWindow : kCdScopeTab, true);
+                              ? kCdScopeWindow : kCdScopeTab, kCdCauseWindow);
       }
       shorten_fnames(true);
     }
@@ -4551,7 +4551,7 @@ static void win_enter_ext(win_T *const wp, const int flags)
     // directory: Change to the global directory.
     if (os_chdir((char *)globaldir) == 0) {
       if (!p_acd && !strequal((char *)globaldir, cwd)) {
-        do_autocmd_dirchanged((char *)globaldir, kCdScopeGlobal, true);
+        do_autocmd_dirchanged((char *)globaldir, kCdScopeGlobal, kCdCauseWindow);
       }
     }
     XFREE_CLEAR(globaldir);