fixes for case-insensitive file systems

exdir/core/exdir_file.py

@@ -125,11 +125,11 @@ def __init__(self, directory, mode=None, allow_remove=False,
 
         # If we have name validation, we need to check for uniqueness.  The
         # directory may exist but with a different case, in which case we
-        # don't want to say that is already exists so that it matches the
+        # don't want to say that it already exists so that it matches the
         # correct checks for the requested mode.
         if name_validation != validation.none:
-            already_exists = validation.path_already_exists_case_insensitive(
-                str(directory.parent), directory.name.lower()
+            already_exists = validation.path_already_exists_case_sensitive(
+                str(directory.parent), directory.name
             )
         else:
             already_exists = directory.exists()

exdir/core/validation.py

@@ -132,3 +132,11 @@ def path_already_exists_case_insensitive(parent_path, name_lower):
         if name_lower == item.lower():
             return True
     return False
+
+
+def path_already_exists_case_sensitive(parent_path, name):
+    # os.listdir is much faster here than os.walk or parent_path.iterdir
+    for item in os.listdir(parent_path):
+        if name == item:
+            return True
+    return False