patch 8.2.1312: MS-Windows: terminal test may fail if dir.exe exists

Problem:    MS-Windows: terminal test may fail if dir.exe exists.
Solution:   Use dir.com. (Ken Takata, closes #6557)

Author: brammool

src/testdir/test_terminal3.vim

@@ -43,15 +43,18 @@ func Test_terminal_shell_option()
     bwipe!
   elseif has('win32')
     " dir is a shell builtin command, should fail without a shell.
+    " However, if dir.exe (which might be provided by Cygwin/MSYS2) exists in
+    " the %PATH%, "term dir" succeeds unintentionally.  Use dir.com instead.
     try
-      term dir /b runtest.vim
-      call WaitForAssert({-> assert_match('job failed\|cannot access .*: No such file or directory', term_getline(bufnr(), 1))})
+      term dir.com /b runtest.vim
+      call WaitForAssert({-> assert_match('job failed', term_getline(bufnr(), 1))})
     catch /CreateProcess/
       " ignore
     endtry
     bwipe!
 
-    term ++shell dir /b runtest.vim
+    " This should execute the dir builtin command even with ".com".
+    term ++shell dir.com /b runtest.vim
     call WaitForAssert({-> assert_match('runtest.vim', term_getline(bufnr(), 1))})
     bwipe!
   endif

src/version.c

@@ -754,6 +754,8 @@ static char *(features[]) =
 
 static int included_patches[] =
 {   /* Add new patch number below this line */
+/**/
+    1312,
 /**/
     1311,
 /**/