Fix Index.repeat for datetime64 types (#15722)

Fixes: #15720 

This PR fixes `Index.repeat` where the `freq` of `DatetimeIndex` needs to be reset.

Authors:
  - GALI PREM SAGAR (https://github.com/galipremsagar)

Approvers:
  - Matthew Roeschke (https://github.com/mroeschke)

URL: #15722

python/cudf/cudf/core/index.py

@@ -2373,6 +2373,11 @@ def tz_convert(self, tz: str | None):
         result_col = self._column.tz_convert(tz)
         return DatetimeIndex._from_data({self.name: result_col})
 
+    def repeat(self, repeats, axis=None):
+        res = super().repeat(repeats, axis=axis)
+        res._freq = None
+        return res
+
 
 class TimedeltaIndex(Index):
     """

python/cudf/cudf/core/indexed_frame.py

@@ -4871,13 +4871,16 @@ def repeat(self, repeats, axis=None):
         1    2
         dtype: int64
         """
-        return self._from_columns_like_self(
+        res = self._from_columns_like_self(
             Frame._repeat(
                 [*self._index._data.columns, *self._columns], repeats, axis
             ),
             self._column_names,
             self._index_names,
         )
+        if isinstance(res.index, cudf.DatetimeIndex):
+            res.index._freq = None
+        return res
 
     def astype(
         self,

python/cudf/cudf/tests/test_index.py

@@ -3252,3 +3252,17 @@ def test_Index_init_with_nans():
     assert gi.dtype == np.dtype("float64")
     pi = pd.Index([1, 2, 3, np.nan])
     assert_eq(pi, gi)
+
+
+def test_index_datetime_repeat():
+    gidx = cudf.date_range("2021-01-01", periods=3, freq="D")
+    pidx = gidx.to_pandas()
+
+    actual = gidx.repeat(5)
+    expected = pidx.repeat(5)
+
+    assert_eq(actual, expected)
+
+    actual = gidx.to_frame().repeat(5)
+
+    assert_eq(actual.index, expected)