patch 8.2.0239: MS-Windows: 'env' job option does not override existing vars

Problem:    MS-Windows: 'env' job option does not override existing
            environment variables.  (Tim Pope)
Solution:   Set the environment variables later. (Yasuhiro Matsumoto,
            closes #5485, closes #5608)

src/os_win32.c

@@ -4948,24 +4948,6 @@ win32_build_env(dict_T *env, garray_T *gap, int is_terminal)
     if (ga_grow(gap, 1) == FAIL)
 	return;
 
-    if (base)
-    {
-	WCHAR	*p = (WCHAR*) base;
-
-	// for last \0
-	if (ga_grow(gap, 1) == FAIL)
-	    return;
-
-	while (*p != 0 || *(p + 1) != 0)
-	{
-	    if (ga_grow(gap, 1) == OK)
-		*((WCHAR*)gap->ga_data + gap->ga_len++) = *p;
-	    p++;
-	}
-	FreeEnvironmentStrings(base);
-	*((WCHAR*)gap->ga_data + gap->ga_len++) = L'\0';
-    }
-
     if (env != NULL)
     {
 	for (hi = env->dv_hashtab.ht_array; todo > 0; ++hi)
@@ -4997,6 +4979,24 @@ win32_build_env(dict_T *env, garray_T *gap, int is_terminal)
 	}
     }
 
+    if (base)
+    {
+	WCHAR	*p = (WCHAR*) base;
+
+	// for last \0
+	if (ga_grow(gap, 1) == FAIL)
+	    return;
+
+	while (*p != 0 || *(p + 1) != 0)
+	{
+	    if (ga_grow(gap, 1) == OK)
+		*((WCHAR*)gap->ga_data + gap->ga_len++) = *p;
+	    p++;
+	}
+	FreeEnvironmentStrings(base);
+	*((WCHAR*)gap->ga_data + gap->ga_len++) = L'\0';
+    }
+
 # if defined(FEAT_CLIENTSERVER) || defined(FEAT_TERMINAL)
     {
 #  ifdef FEAT_CLIENTSERVER

src/testdir/test_channel.vim

@@ -2006,3 +2006,12 @@ func Test_issue_5150()
   sleep 10m
   call assert_equal(-1, job_info(g:job).exitval)
 endfunc
+
+func Test_issue_5485()
+  let $VAR1 = 'global'
+  let g:Ch_reply = ""
+  let l:job = job_start([&shell, &shellcmdflag, has('win32') ? 'echo %VAR1% %VAR2%' : 'echo $VAR1 $VAR2'], {'env': {'VAR1': 'local', 'VAR2': 'local'}, 'callback': 'Ch_handler'})
+  let g:Ch_job = l:job
+  call WaitForAssert({-> assert_equal("local local", trim(g:Ch_reply))})
+  unlet $VAR1
+endfunc

src/version.c

@@ -742,6 +742,8 @@ static char *(features[]) =
 
 static int included_patches[] =
 {   /* Add new patch number below this line */
+/**/
+    239,
 /**/
     238,
 /**/