Fix mv bug: Should be able to stat files, but not able to mv if source and target are the same (#2763)

Closes #2760

tests/by-util/test_mv.rs

@@ -232,6 +232,40 @@ fn test_mv_force_replace_file() {
     assert!(at.file_exists(file_b));
 }
 
+#[test]
+fn test_mv_same_file() {
+    let (at, mut ucmd) = at_and_ucmd!();
+    let file_a = "test_mv_same_file_a";
+
+    at.touch(file_a);
+    ucmd.arg(file_a).arg(file_a).fails().stderr_is(format!(
+        "mv: '{f}' and '{f}' are the same file\n",
+        f = file_a,
+    ));
+}
+
+#[test]
+fn test_mv_same_file_not_dot_dir() {
+    let (at, mut ucmd) = at_and_ucmd!();
+    let dir = "test_mv_errors_dir";
+
+    at.mkdir(dir);
+    ucmd.arg(dir).arg(dir).fails().stderr_is(format!(
+        "mv: cannot move '{d}' to a subdirectory of itself, '{d}/{d}'",
+        d = dir,
+    ));
+}
+
+#[test]
+fn test_mv_same_file_dot_dir() {
+    let (_at, mut ucmd) = at_and_ucmd!();
+
+    ucmd.arg(".")
+        .arg(".")
+        .fails()
+        .stderr_is("mv: '.' and '.' are the same file\n".to_string());
+}
+
 #[test]
 fn test_mv_simple_backup() {
     let (at, mut ucmd) = at_and_ucmd!();