cmd/tests: Correctly determine script path for root directories.

programs/cmd/tests/batch.c

@@ -459,8 +459,14 @@ START_TEST(batch)
     drive[0] = workdir[0];
     drive[1] = workdir[1]; /* Should be ':' */
     memcpy(path, workdir + drive_len, (workdir_len - drive_len) * sizeof(drive[0]));
-    path[workdir_len - drive_len] = '\\';
-    path_len = workdir_len - drive_len + 1;
+
+    /* Only add trailing backslash to 'path' for non-root directory */
+    if (workdir_len - drive_len > 1) {
+        path[workdir_len - drive_len] = '\\';
+        path_len = workdir_len - drive_len + 1;
+    } else {
+        path_len = 1; /* \ */
+    }
     shortpath_len = GetShortPathNameA(path, shortpath,
                                       sizeof(shortpath)/sizeof(shortpath[0]));
 

programs/cmd/tests/test_builtins.cmd

@@ -308,6 +308,13 @@ set WINE_FOO=
 
 echo ------------ Testing variable expansion ------------
 call :setError 0
+echo ~p0 should be path containing batch file
+echo %~p0
+mkdir dummydir
+cd dummydir
+echo %~p0
+cd ..
+rmdir dummydir
 echo ~dp0 should be directory containing batch file
 echo %~dp0
 mkdir dummydir

programs/cmd/tests/test_builtins.cmd.exp

@@ -259,6 +259,9 @@ foo
 'jim'
 'apple"banana"grape'
 ------------ Testing variable expansion ------------
+~p0 should be path containing batch file
+@path@
+@path@
 ~dp0 should be directory containing batch file
 @pwd@\
 @pwd@\