diff --git a/git/objects/tree.py b/git/objects/tree.py
index 450973280..a08adf48b 100644
--- a/git/objects/tree.py
+++ b/git/objects/tree.py
@@ -53,6 +53,54 @@
 __all__ = ("TreeModifier", "Tree")
 
 
+def git_cmp(t1: TreeCacheTup, t2: TreeCacheTup) -> int:
+    a, b = t1[2], t2[2]
+    # assert isinstance(a, str) and isinstance(b, str)
+    len_a, len_b = len(a), len(b)
+    min_len = min(len_a, len_b)
+    min_cmp = cmp(a[:min_len], b[:min_len])
+
+    if min_cmp:
+        return min_cmp
+
+    return len_a - len_b
+
+
+def merge_sort(a: List[TreeCacheTup], cmp: Callable[[TreeCacheTup, TreeCacheTup], int]) -> None:
+    if len(a) < 2:
+        return
+
+    mid = len(a) // 2
+    lefthalf = a[:mid]
+    righthalf = a[mid:]
+
+    merge_sort(lefthalf, cmp)
+    merge_sort(righthalf, cmp)
+
+    i = 0
+    j = 0
+    k = 0
+
+    while i < len(lefthalf) and j < len(righthalf):
+        if cmp(lefthalf[i], righthalf[j]) <= 0:
+            a[k] = lefthalf[i]
+            i = i + 1
+        else:
+            a[k] = righthalf[j]
+            j = j + 1
+        k = k + 1
+
+    while i < len(lefthalf):
+        a[k] = lefthalf[i]
+        i = i + 1
+        k = k + 1
+
+    while j < len(righthalf):
+        a[k] = righthalf[j]
+        j = j + 1
+        k = k + 1
+
+
 class TreeModifier:
     """A utility class providing methods to alter the underlying cache in a list-like fashion.
 
@@ -83,7 +131,7 @@ def set_done(self) -> "TreeModifier":
 
         :return self:
         """
-        self._cache.sort(key=lambda x: (x[2] + "/") if x[1] == Tree.tree_id << 12 else x[2])
+        merge_sort(self._cache, git_cmp)
         return self
 
     # } END interface