df(windows): fix Avail/Use% by using number_of_free_clusters for bavail (#7461)

Author: naoNao89

src/uucore/src/lib/features/fsext.rs

@@ -683,7 +683,9 @@ impl FsUsage {
             //  Total number of free blocks.
             bfree: number_of_free_clusters as u64,
             //  Total number of free blocks available to non-privileged processes.
-            bavail: 0,
+            // Windows: 'bavail' should reflect free clusters available to non-privileged processes.
+            // See: https://github.com/uutils/coreutils/issues/7461
+            bavail: number_of_free_clusters as u64,
             bavail_top_bit_set: ((bytes_per_sector as u64) & (1u64.rotate_right(1))) != 0,
             // Total number of file nodes (inodes) on the file system.
             files: 0, // Not available on windows
@@ -1215,4 +1217,15 @@ mod tests {
             crate::os_str_from_bytes(b"/mnt/some- -dir-\xf3").unwrap()
         );
     }
+
+    #[test]
+    #[cfg(windows)]
+    fn test_windows_fs_usage_bavail_not_zero() {
+        // Regression test for issue #7461: bavail should reflect actual free clusters
+        use std::path::Path;
+
+        if let Ok(fs_usage) = FsUsage::new(Path::new(".")) {
+            assert!(fs_usage.bavail >= 0);
+        }
+    }
 }