patch 8.2.3378: MS-Windows: completing environment variables with % is wrong

Problem:    MS-Windows: completing environment variables with % is wrong.
Solution:   Only complete environment variables with $. (Albert Liu,
            closes #8791)

src/cmdexpand.c

@@ -1277,12 +1277,8 @@ set_one_cmd_context(
 		xp->xp_context = EXPAND_SHELLCMD;
 	}
 
-	// Check for environment variable
-	if (*xp->xp_pattern == '$'
-#if defined(MSWIN)
-		|| *xp->xp_pattern == '%'
-#endif
-		)
+	// Check for environment variable.
+	if (*xp->xp_pattern == '$')
 	{
 	    for (p = xp->xp_pattern + 1; *p != NUL; ++p)
 		if (!vim_isIDc(*p))
@@ -1296,7 +1292,7 @@ set_one_cmd_context(
 		    compl = EXPAND_ENV_VARS;
 	    }
 	}
-	// Check for user names
+	// Check for user names.
 	if (*xp->xp_pattern == '~')
 	{
 	    for (p = xp->xp_pattern + 1; *p != NUL && *p != '/'; ++p)

src/testdir/test_cmdline.vim

@@ -9,6 +9,10 @@ func Test_complete_tab()
   call writefile(['testfile'], 'Xtestfile')
   call feedkeys(":e Xtest\t\r", "tx")
   call assert_equal('testfile', getline(1))
+
+  " Pressing <Tab> after '%' completes the current file, also on MS-Windows
+  call feedkeys(":e %\t\r", "tx")
+  call assert_equal('e Xtestfile', @:)
   call delete('Xtestfile')
 endfunc
 

src/version.c

@@ -755,6 +755,8 @@ static char *(features[]) =
 
 static int included_patches[] =
 {   /* Add new patch number below this line */
+/**/
+    3378,
 /**/
     3377,
 /**/